CA2582395C - High density wlan system - Google Patents
High density wlan system Download PDFInfo
- Publication number
- CA2582395C CA2582395C CA2582395A CA2582395A CA2582395C CA 2582395 C CA2582395 C CA 2582395C CA 2582395 A CA2582395 A CA 2582395A CA 2582395 A CA2582395 A CA 2582395A CA 2582395 C CA2582395 C CA 2582395C
- Authority
- CA
- Canada
- Prior art keywords
- threshold
- access point
- clear channel
- channel assessment
- packet
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Active
Links
Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W16/00—Network planning, e.g. coverage or traffic planning tools; Network deployment, e.g. resource partitioning or cells structures
- H04W16/02—Resource partitioning among network components, e.g. reuse partitioning
- H04W16/06—Hybrid resource partitioning, e.g. channel borrowing
- H04W16/08—Load shedding arrangements
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W84/00—Network topologies
- H04W84/02—Hierarchically pre-organised networks, e.g. paging networks, cellular networks, WLAN [Wireless Local Area Network] or WLL [Wireless Local Loop]
- H04W84/10—Small scale networks; Flat hierarchical networks
- H04W84/12—WLAN [Wireless Local Area Networks]
Abstract
A method for controlling cell sizes (118a, ..., 118n) associated with respective access points (102a, ..., 102n), each having a receive sensitivity and an output power. The method includes changing the start of packet thresholds and/or clear channel assessment thresholds to vary the cell sizes (I 18a,...,118n) of the access points (102a, ..., 102n).
Description
TITLE OF THE INVENTION
HIGH DENSITY WLAN SYSTEM
BACKGROUND OF THE INVENTION
The present invention relates generally to wireless networks and more particularly to a system and method for a high density wireless local area network.
The popularity of wireless devices is leading to increased user density within wireless local area networks operating in accordance with the Institute of Electrical and Electronics Engineers (IEEE) 802.11 a/b/g standards. However, as more users are added to a given network, the available throughput per user decreases. This is due to the fact that all of the communicated data passes through access points comprising the network, and each access point is limited in data throughput capability.
One approach to increasing throughput, thereby providing for additional users, is to add more access points to the network. This approach is valid provided there are enough carrier frequencies for all of the access points to operate on a different frequency. However, this approach fails when there are no longer any unused carrier frequencies available and carrier frequencies are reused.
For example, if an access point is added on a carrier frequency that is already assigned to another access point, two "cells" operating on the same frequency results.
As used herein, the tenn "cell" describes a single access point and the client devices associated with that access point. Moreover, the additional access point provides no additional throughput if the two cells are in close proximity and the respective service areas of the two access points overlap. No additional throughput results because the carrier sense multiple access (CSMA) mechanism typically used to mitigate interference for IEEE 802.11 products prevents the two -co=channel access points from operating simultaneously.
Despite the carrier sense multiple access mechanism preventing the two co-channel access points from operating simultaneously, in many instances there is adequate signal-to-interference ratio (SIR) to allow simultaneous transmission. As used herein, the signal-to-interference ratio is the ratio of the intended signal power to the total interference signal power originating from other cells. Therefore, it is often desirable to reduce the service areas of access points such that the service areas of co-channel access points do not overlap, thereby increasing throughput.
HIGH DENSITY WLAN SYSTEM
BACKGROUND OF THE INVENTION
The present invention relates generally to wireless networks and more particularly to a system and method for a high density wireless local area network.
The popularity of wireless devices is leading to increased user density within wireless local area networks operating in accordance with the Institute of Electrical and Electronics Engineers (IEEE) 802.11 a/b/g standards. However, as more users are added to a given network, the available throughput per user decreases. This is due to the fact that all of the communicated data passes through access points comprising the network, and each access point is limited in data throughput capability.
One approach to increasing throughput, thereby providing for additional users, is to add more access points to the network. This approach is valid provided there are enough carrier frequencies for all of the access points to operate on a different frequency. However, this approach fails when there are no longer any unused carrier frequencies available and carrier frequencies are reused.
For example, if an access point is added on a carrier frequency that is already assigned to another access point, two "cells" operating on the same frequency results.
As used herein, the tenn "cell" describes a single access point and the client devices associated with that access point. Moreover, the additional access point provides no additional throughput if the two cells are in close proximity and the respective service areas of the two access points overlap. No additional throughput results because the carrier sense multiple access (CSMA) mechanism typically used to mitigate interference for IEEE 802.11 products prevents the two -co=channel access points from operating simultaneously.
Despite the carrier sense multiple access mechanism preventing the two co-channel access points from operating simultaneously, in many instances there is adequate signal-to-interference ratio (SIR) to allow simultaneous transmission. As used herein, the signal-to-interference ratio is the ratio of the intended signal power to the total interference signal power originating from other cells. Therefore, it is often desirable to reduce the service areas of access points such that the service areas of co-channel access points do not overlap, thereby increasing throughput.
2 One approach to reducing the service area of an access point is to reduce or limit the output power of the access point. This approach addresses the problem of overlapping service areas, but also decreases client received signal strength within the service area rates and consequently decreases the signal to noise ratio. Furthermore, since higher data rates require higher received signal strength than lower data rates, the usable range for higher data rates is less than the usable range for lower data rates. Therefore, reducing the output power of access points such that services areas of the cells do not overlap allows co-channel cells to simultaneously transmit, but also reduces the range for higher data rates within the intended service areas. Therefore, controlling cell size by reducing output power also results in limited to throughput, resulting in breaches in the total coverage area, e.g., between the access points, for the higher data rates.
Thus, there exists a need for a system and method for a high density wireless local area network that controls cell size in a way that allows multiple cells on the same carrier frequency to transmit simultaneously, but without reducing the transmit power, thereby preserving the range capability of the higher data rates.
SUMMARY OF THE INVENTION
The present invention provides a system and method for a high density wireless local area network that controls cell size in a way that allows multiple cells on the same carrier frequency to transmit simultaneously, but without reducing the transmit power, thereby preserving the range capability of the higher data rates. More particularly, the present invention controls cell size by varying start of packet (SOP) and/or clear channel assessment (CCA) thresholds.
In accordance with an aspect of the present invention, the threshold signal strength for receiving a packet, e.g., SOP, is varied to increase or decrease the cell size. In accordance with an aspect of the present invention, the threshold for sending a transmission, e.g., CCA, is varied to increase or decrease the cell size.
In accordance with the present invention there is disclosed herein a method for controlling cell size associated with an access point having a receive sensitivity and an output power. The method includes changing at least one of a start of packet threshold and a clear channel assessment threshold to vary the cell size of the access point.
Further in accordance with the present invention there is disclosed herein a method for operating a high density wireless local area network. The method includes assigning multiple access points having receive sensitivities and output powers to the same carrier
Thus, there exists a need for a system and method for a high density wireless local area network that controls cell size in a way that allows multiple cells on the same carrier frequency to transmit simultaneously, but without reducing the transmit power, thereby preserving the range capability of the higher data rates.
SUMMARY OF THE INVENTION
The present invention provides a system and method for a high density wireless local area network that controls cell size in a way that allows multiple cells on the same carrier frequency to transmit simultaneously, but without reducing the transmit power, thereby preserving the range capability of the higher data rates. More particularly, the present invention controls cell size by varying start of packet (SOP) and/or clear channel assessment (CCA) thresholds.
In accordance with an aspect of the present invention, the threshold signal strength for receiving a packet, e.g., SOP, is varied to increase or decrease the cell size. In accordance with an aspect of the present invention, the threshold for sending a transmission, e.g., CCA, is varied to increase or decrease the cell size.
In accordance with the present invention there is disclosed herein a method for controlling cell size associated with an access point having a receive sensitivity and an output power. The method includes changing at least one of a start of packet threshold and a clear channel assessment threshold to vary the cell size of the access point.
Further in accordance with the present invention there is disclosed herein a method for operating a high density wireless local area network. The method includes assigning multiple access points having receive sensitivities and output powers to the same carrier
3 frequency and controlling cell sizes associated with the access points by changing at least one of a start of packet threshold and a clear channel assessment threshold to vary the cell sizes of the access points.
Still further in accordance with the present invention there is disclosed herein an access point configured to implement a methodology of the present invention.
The access point comprises a transceiver configured for engaging in wireless communications with clients and a controller a controller coupled to the transceiver and configured to control the operation of the transceiver when engaging in wireless communications with the clients. The transceiver includes a transmitter having an output power and a receiver having a receive sensitivity, while the controller includes a processor configured for executing program code and a memory configured for storing the program code and a start of packet threshold or a clear channel assessment threshold. The start of packet threshold or the clear channel assessment threshold is varied to control the cell size of the access point.
Yet further in accordance with the present invention there is disclosed herein a high density wireless local area network. The network includes a first access point and second access points assigned to the same carrier frequency. Each access point includes a transmitter having an output power, a receiver having a receive sensitivity, a processor configured for executing program code to control the operation of the transmitter and the receiver when engaging in wireless communications with clients, and a memory configured for storing the program code and a start of packet threshold or a clear channel assessment threshold. Cell sizes associated with the first and second access points are controlled by changing at the start of packet thresholds or the clear channel assessment thresholds to vary the cells sizes of the access points.
By virtue of the foregoing, there is thus provided a system and method for a high density wireless local area network that controls cell size in a way that allows multiple cells on the same carrier frequency to transmit simultaneously, but without reducing the transmit power, thereby preserving the range capability of the higher data rates.
These and other objects and advantages of the present invention will become readily apparent to those skilled in this art from the following description wherein there is shown and described a preferred embodiment of this invention, simply by way of illustration of one of the best modes suited to carry out the invention. As it will be realized, the invention is capable of other different embodiments and its several details are capable of modifications in various obvious aspects all without departing from the spirit of the present invention.
Still further in accordance with the present invention there is disclosed herein an access point configured to implement a methodology of the present invention.
The access point comprises a transceiver configured for engaging in wireless communications with clients and a controller a controller coupled to the transceiver and configured to control the operation of the transceiver when engaging in wireless communications with the clients. The transceiver includes a transmitter having an output power and a receiver having a receive sensitivity, while the controller includes a processor configured for executing program code and a memory configured for storing the program code and a start of packet threshold or a clear channel assessment threshold. The start of packet threshold or the clear channel assessment threshold is varied to control the cell size of the access point.
Yet further in accordance with the present invention there is disclosed herein a high density wireless local area network. The network includes a first access point and second access points assigned to the same carrier frequency. Each access point includes a transmitter having an output power, a receiver having a receive sensitivity, a processor configured for executing program code to control the operation of the transmitter and the receiver when engaging in wireless communications with clients, and a memory configured for storing the program code and a start of packet threshold or a clear channel assessment threshold. Cell sizes associated with the first and second access points are controlled by changing at the start of packet thresholds or the clear channel assessment thresholds to vary the cells sizes of the access points.
By virtue of the foregoing, there is thus provided a system and method for a high density wireless local area network that controls cell size in a way that allows multiple cells on the same carrier frequency to transmit simultaneously, but without reducing the transmit power, thereby preserving the range capability of the higher data rates.
These and other objects and advantages of the present invention will become readily apparent to those skilled in this art from the following description wherein there is shown and described a preferred embodiment of this invention, simply by way of illustration of one of the best modes suited to carry out the invention. As it will be realized, the invention is capable of other different embodiments and its several details are capable of modifications in various obvious aspects all without departing from the spirit of the present invention.
4 Accordingly, the drawings and descriptions will be regarded as illustrative in nature and not as restrictive.
BRIEF DESCRIPTION OF THE DRAWINGS
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the present invention and, together with a general description of the invention given above, and the detailed description given below, serve to explain the principles of the present invention.
Figure 1 is a block diagram of a wireless local area network including a number of access points in accordance with principles of the present invention;
Figure 2 is an illustration of a scenario for a wireless network including four access points with three available frequencies;
Figure 3 is an illustration of how start of packet and clear channel assessment thresholds control cell size;
Figure 4 is a graph showing the relationship between start of packet and clear channel assessment thresholds and client signal strength;
Figure 5 is a graph showing the divergence of throughput density when the start of packet and clear channel assessment thresholds are set to the minimum receive sensitivity from ideal throughput density as access point density increases;
Figure 6 is a graphical depiction of access point ranges for various data rates for an access point operated at nominal power;
Figure 7 is a graphical depiction of controlling cell size by reducing output power;
and Figure 8 is a graphical depiction of controlling cell size by increasing and/or setting the start of packet and/or the clear channel assessment thresholds in accordance with principles of the present invention.
DETAILED DESCRIPTION OF THE DRAWINGS
With reference to Figure 1, one embodiment 100 of a wireless network in accordance with principles of the present invention is shown. For example, wireless local area network 100 operates in accordance with one or more of the Institute of Electrical and Electronics Engineers (IEEE) 802.11 a/b/g standards in any one of a number of designated frequency bands using a number of similarly designated carrier frequencies or channels.
Such carrier frequencies or channels are typically limited in number, for example, numbering as few as three and as many as twenty-three in the United States of America.
BRIEF DESCRIPTION OF THE DRAWINGS
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the present invention and, together with a general description of the invention given above, and the detailed description given below, serve to explain the principles of the present invention.
Figure 1 is a block diagram of a wireless local area network including a number of access points in accordance with principles of the present invention;
Figure 2 is an illustration of a scenario for a wireless network including four access points with three available frequencies;
Figure 3 is an illustration of how start of packet and clear channel assessment thresholds control cell size;
Figure 4 is a graph showing the relationship between start of packet and clear channel assessment thresholds and client signal strength;
Figure 5 is a graph showing the divergence of throughput density when the start of packet and clear channel assessment thresholds are set to the minimum receive sensitivity from ideal throughput density as access point density increases;
Figure 6 is a graphical depiction of access point ranges for various data rates for an access point operated at nominal power;
Figure 7 is a graphical depiction of controlling cell size by reducing output power;
and Figure 8 is a graphical depiction of controlling cell size by increasing and/or setting the start of packet and/or the clear channel assessment thresholds in accordance with principles of the present invention.
DETAILED DESCRIPTION OF THE DRAWINGS
With reference to Figure 1, one embodiment 100 of a wireless network in accordance with principles of the present invention is shown. For example, wireless local area network 100 operates in accordance with one or more of the Institute of Electrical and Electronics Engineers (IEEE) 802.11 a/b/g standards in any one of a number of designated frequency bands using a number of similarly designated carrier frequencies or channels.
Such carrier frequencies or channels are typically limited in number, for example, numbering as few as three and as many as twenty-three in the United States of America.
5 Wireless local area network 100 is defined by a plurality of access points 102a-n, access point 102a being shown in block diagram form, where "n" is an integer greater than one and denotes any practical number of access points. The carrier frequencies are generally assigned to the access points 102a-n for use in wireless data communications.
However, as the number of access points 102a-n is often greater than the number of carrier frequencies afford by the standards, carrier frequencies or channels are reused, resulting in multiple access points operating on the same channel or co-channel access points.
More specifically, the access points 102a-n are configured to engage in wireless data communications, an exemplary communication link being shown at reference numeral 106, with a number of wireless devices designated as clients 104a-m, where "m" as shown is an integer greater than one and denotes any number of clients, and n and m can be equal or unequal. The popularity of these wireless devices leads to increased user density within the wireless local area network 100 as more clients 104a-m are added to the wireless local area network 100.
The access points 102a-n are placed in communication via a fixed backbone network 108. Access points 102a-n define cells 118a-n respectively, not drawn to scale. The operations of access points 102a-n are, in part, controlled by a server 110, also placed in communication with the access points 102a-n via the fixed backbone network 108. Each of the access points 102a-n generally include a transceiver 112a for engaging in wireless data communications with the clients 104a-m. More specifically, each transceiver 112a comprises a transmitter 114a for transmitting data to and a receiver 11 6a for receiving data from the clients 104a-m. The operation of transceiver 112a is controlled by a controller 120a.
Controller 120a comprises a processor 122a, e.g., a central processing unit such as a microprocessor, and a memory 124a. Memory 124a suitably comprises at least one of read only memory (e.g., a non-volatile memory such as a ROM, CD ROM, EEPROM) and volatile memory such as random access memory. Program code and configurable operating parameters (e.g., SOP, CCA) for controlling the operation of processor 122a are stored in memory 124a or other computer-readable medium. Data path 126a is employed for transferring data between processor 122a, memory 124a, transmitter 11 4a and receiver 114a.
However, as the number of access points 102a-n is often greater than the number of carrier frequencies afford by the standards, carrier frequencies or channels are reused, resulting in multiple access points operating on the same channel or co-channel access points.
More specifically, the access points 102a-n are configured to engage in wireless data communications, an exemplary communication link being shown at reference numeral 106, with a number of wireless devices designated as clients 104a-m, where "m" as shown is an integer greater than one and denotes any number of clients, and n and m can be equal or unequal. The popularity of these wireless devices leads to increased user density within the wireless local area network 100 as more clients 104a-m are added to the wireless local area network 100.
The access points 102a-n are placed in communication via a fixed backbone network 108. Access points 102a-n define cells 118a-n respectively, not drawn to scale. The operations of access points 102a-n are, in part, controlled by a server 110, also placed in communication with the access points 102a-n via the fixed backbone network 108. Each of the access points 102a-n generally include a transceiver 112a for engaging in wireless data communications with the clients 104a-m. More specifically, each transceiver 112a comprises a transmitter 114a for transmitting data to and a receiver 11 6a for receiving data from the clients 104a-m. The operation of transceiver 112a is controlled by a controller 120a.
Controller 120a comprises a processor 122a, e.g., a central processing unit such as a microprocessor, and a memory 124a. Memory 124a suitably comprises at least one of read only memory (e.g., a non-volatile memory such as a ROM, CD ROM, EEPROM) and volatile memory such as random access memory. Program code and configurable operating parameters (e.g., SOP, CCA) for controlling the operation of processor 122a are stored in memory 124a or other computer-readable medium. Data path 126a is employed for transferring data between processor 122a, memory 124a, transmitter 11 4a and receiver 114a.
6 Data path 126a is at least one of a wired and wired communication link suitable for transferring data between the aforementioned components.
The term "computer-readable medium" as used herein refers to any medium that participates in providing instructions to processor 122a for execution. Such a medium may take many forms, including but not limited to non-volatile media, volatile media, and transmission media. Non-volatile media include for example optical or magnetic disks.
Volatile media include dynamic memory such as main memory 124a. Transmission media include coaxial cables, copper wire and fiber optics, including the wires that data path 126a.
Transmission media can also take the form of acoustic or light waves such as those generated during radio frequency (RF) and infrared (IR) data communications. Common forms of computer-readable media include for example floppy disk, a flexible disk, hard disk, magnetic cards, paper tape, any other physical medium with patterns of holes, a RAM, a PROM, an EPROM, a FLASHPROM, any other memory chip or cartridge, a carrier wave as described hereinafter, or any other medium from which a computer can read.
Various forms of computer-readable media may be involved in carrying one or more sequences of one or more instructions to processor 122a for execution. For example, the instructions may initially be borne on a magnetic disk of a remote computer.
The remote computer can load the instructions into its dynamic memory and send the instructions over a telephone line using a modem. A modem local to computer system can receive the data on the telephone line and use an infrared transmitter to convert the data to an infrared signal. An infrared detector coupled to data path 126a can receive the data carried in the infrared signal and place the data on data path 126a. Data path 126a carries the data to main memory 124a from which processor 122a retrieves and executes the instructions. The instructions received by main memory 124a may optionally be stored on a storage device either before or after execution by processor 122a.
Wireless data communications between the access points 102a-n and the clients 104a-m occur at a variety of different data rates, such as, for example, 6, 9, 12, 18, 24, 36, 48, and 54 Megabits per second (Mbps), as necessitated by the applications used by the clients 104a-m and the capabilities of the access points 102a-n. Thus, from time to time, the clients 104a-m and the access points 102a-n engage in high data rate communications, e.g., 54 Megabits per second, and low data rate communications, e.g., 6 Megabits per second. As will be appreciated by the skilled artisan, higher data rates require higher received signal strength than lower data rates. Thus, the usable range for higher data rates is less than the usable
The term "computer-readable medium" as used herein refers to any medium that participates in providing instructions to processor 122a for execution. Such a medium may take many forms, including but not limited to non-volatile media, volatile media, and transmission media. Non-volatile media include for example optical or magnetic disks.
Volatile media include dynamic memory such as main memory 124a. Transmission media include coaxial cables, copper wire and fiber optics, including the wires that data path 126a.
Transmission media can also take the form of acoustic or light waves such as those generated during radio frequency (RF) and infrared (IR) data communications. Common forms of computer-readable media include for example floppy disk, a flexible disk, hard disk, magnetic cards, paper tape, any other physical medium with patterns of holes, a RAM, a PROM, an EPROM, a FLASHPROM, any other memory chip or cartridge, a carrier wave as described hereinafter, or any other medium from which a computer can read.
Various forms of computer-readable media may be involved in carrying one or more sequences of one or more instructions to processor 122a for execution. For example, the instructions may initially be borne on a magnetic disk of a remote computer.
The remote computer can load the instructions into its dynamic memory and send the instructions over a telephone line using a modem. A modem local to computer system can receive the data on the telephone line and use an infrared transmitter to convert the data to an infrared signal. An infrared detector coupled to data path 126a can receive the data carried in the infrared signal and place the data on data path 126a. Data path 126a carries the data to main memory 124a from which processor 122a retrieves and executes the instructions. The instructions received by main memory 124a may optionally be stored on a storage device either before or after execution by processor 122a.
Wireless data communications between the access points 102a-n and the clients 104a-m occur at a variety of different data rates, such as, for example, 6, 9, 12, 18, 24, 36, 48, and 54 Megabits per second (Mbps), as necessitated by the applications used by the clients 104a-m and the capabilities of the access points 102a-n. Thus, from time to time, the clients 104a-m and the access points 102a-n engage in high data rate communications, e.g., 54 Megabits per second, and low data rate communications, e.g., 6 Megabits per second. As will be appreciated by the skilled artisan, higher data rates require higher received signal strength than lower data rates. Thus, the usable range for higher data rates is less than the usable
7 range for lower data rates. The usable range for various data rates with respect to cell size will be described in more detail hereinafter.
To mitigate interfere between the cells 118a-o, the access points 102a-m include a carrier sense multiple access (CSMA) mechanism for performing clear channel assessment.
To this end, each of the access points further includes a controller 120a for controlling the operation of transceiver 112a when engaging in wireless data communications with the clients 104a-m. More specifically, each controller 120a comprises a processor 122a and a memory 124a. Processor 122a is configured for executing program code stored in memory 124a, while memory 124a also stores thresholds as will now be described.
The start of packet (SOP) threshold denotes a limit that the receiver 116a uses to decide if a particular data packet should be received or not. For example, the receiver 116a will demodulate a packet if the signal strength of the packet is at or above the start of packet threshold and will ignore the packet otherwise. Similarly, the clear channel assessment (CCA) threshold denotes a limit that controls when the transmitter 114a transmits. For example, if the access point 102a wishes to transmit, the transceiver 11 2a uses the receiver 11 6a to monitor a respective channel to determine if there is any signal energy above the clear channel assessment threshold. The transmitter 114a transmits if the signal energy is below the clear channel assessment threshold, and refrains from transmitting otherwise. Thus, the start of packet and clear channel assessment thresholds can be controlled separately.
The start of packet and clear channel assessment thresholds are set to initial values.
However, in accordance with principles of the present invention, and as will be described in more detail hereinafter, the start of packet threshold and/or the clear channel assessment threshold are varied to control cell size in a way that allows multiple cells on the same carrier frequency to transmit simultaneously, without reducing or otherwise changing the transmit power, thereby maintaining the signal to noise ratio and signal to interference ratio, preserving the range capability for higher data rates.
For purposes and ease of illustration, Figure 2 shows a scenario 200 where four access points 202a-d having four respective intended service areas 208a-d (shown in dashed line) are deployed to cover an area 204, but there are only three carrier frequencies or channels, denoted as Fl-F3, available for use. Because there are only three frequencies FI-F3 available for use, two of the access points, e.g., access points 202a and 202d, are assigned or operate on the same carrier frequency or channel Fl.
Furthermore, suppose that the desired throughput per user requires an access point every fifty feet as generally indicated at reference numeral 206. Thus, in this scenario 200,
To mitigate interfere between the cells 118a-o, the access points 102a-m include a carrier sense multiple access (CSMA) mechanism for performing clear channel assessment.
To this end, each of the access points further includes a controller 120a for controlling the operation of transceiver 112a when engaging in wireless data communications with the clients 104a-m. More specifically, each controller 120a comprises a processor 122a and a memory 124a. Processor 122a is configured for executing program code stored in memory 124a, while memory 124a also stores thresholds as will now be described.
The start of packet (SOP) threshold denotes a limit that the receiver 116a uses to decide if a particular data packet should be received or not. For example, the receiver 116a will demodulate a packet if the signal strength of the packet is at or above the start of packet threshold and will ignore the packet otherwise. Similarly, the clear channel assessment (CCA) threshold denotes a limit that controls when the transmitter 114a transmits. For example, if the access point 102a wishes to transmit, the transceiver 11 2a uses the receiver 11 6a to monitor a respective channel to determine if there is any signal energy above the clear channel assessment threshold. The transmitter 114a transmits if the signal energy is below the clear channel assessment threshold, and refrains from transmitting otherwise. Thus, the start of packet and clear channel assessment thresholds can be controlled separately.
The start of packet and clear channel assessment thresholds are set to initial values.
However, in accordance with principles of the present invention, and as will be described in more detail hereinafter, the start of packet threshold and/or the clear channel assessment threshold are varied to control cell size in a way that allows multiple cells on the same carrier frequency to transmit simultaneously, without reducing or otherwise changing the transmit power, thereby maintaining the signal to noise ratio and signal to interference ratio, preserving the range capability for higher data rates.
For purposes and ease of illustration, Figure 2 shows a scenario 200 where four access points 202a-d having four respective intended service areas 208a-d (shown in dashed line) are deployed to cover an area 204, but there are only three carrier frequencies or channels, denoted as Fl-F3, available for use. Because there are only three frequencies FI-F3 available for use, two of the access points, e.g., access points 202a and 202d, are assigned or operate on the same carrier frequency or channel Fl.
Furthermore, suppose that the desired throughput per user requires an access point every fifty feet as generally indicated at reference numeral 206. Thus, in this scenario 200,
8 the co-channel access points 202a and 202d are separated by one hundred fifty feet as indicated at reference numeral 210. Although the intended service area radius for each access point is approximately fifty feet, as indicated at reference numeral 212a, the typical range of an 802.11 wireless local area network transceiver, e.g., transceiver 112a shown in Figure 1, is on the order of several hundred feet or more for lower data rates, as indicated at reference numera1214a. Therefore, the actual service area 216a of access point 202a encompasses the intended service area 208d of access point 202d. Similarly, the actual service area (not shown) of access point 202d encompasses the intended service area 208a of access point 202a. In addition, if the start of packet and clear channel assessment thresholds are set to initial receive sensitivities of the transceivers, as defined by the receivers, and used by the carrier sense multiple access mechanisms within the access points 202a, 202d, only one of the two access points can be active at a given time and the combined throughput for both access points will be no greater than the maximum throughput of a single access point.
However, if the start of packet threshold and/or the clear channel assessment threshold are changed and/or varied in accordance with principles of the present invention, both of the access points 202a, 202d can be active at a given time and the combined throughput for both access points will be greater than the maximum throughput of a single access point, e.g., twice that of a single access point. Moreover, the intended service areas 208a-d of the access points 202a-d can be realized.
Figure 3 shows how varying the start of packet and clear channel assessment thresholds is used to control cell size. Generally, cel1300 is defined by access point 302 and client 304. As shown, cell 300 has a first service area 306 and a second service area 308.
The first service area 306 has increased SOP and CCA thresholds when compared to the second service area 308. Thus, because the first service area 306 has a higher the start of packet and clear channel assessment thresholds, access point 302 ignores signals from client 304, as client 304 is outside the service area 306. Conversely, because service area 308 has lower start of packet and clear channel assessment thresholds, access point 302 processes signals from client 304, as client 304 is inside the service area 308. Thus, raising and lowering the start of packet and clear channel assessment thresholds can be used to control cell size.
Figure 4 shows a graph 400 illustrating the relationship between start of packet and clear channel assessment thresholds and client signal strength. As shown, the x-axis, or ordinate, generally indicates time, while the y-axis, or abscissa, indicates signal strength. A
client signal strength is indicated at reference numeral 402. As indicated at reference numeral
However, if the start of packet threshold and/or the clear channel assessment threshold are changed and/or varied in accordance with principles of the present invention, both of the access points 202a, 202d can be active at a given time and the combined throughput for both access points will be greater than the maximum throughput of a single access point, e.g., twice that of a single access point. Moreover, the intended service areas 208a-d of the access points 202a-d can be realized.
Figure 3 shows how varying the start of packet and clear channel assessment thresholds is used to control cell size. Generally, cel1300 is defined by access point 302 and client 304. As shown, cell 300 has a first service area 306 and a second service area 308.
The first service area 306 has increased SOP and CCA thresholds when compared to the second service area 308. Thus, because the first service area 306 has a higher the start of packet and clear channel assessment thresholds, access point 302 ignores signals from client 304, as client 304 is outside the service area 306. Conversely, because service area 308 has lower start of packet and clear channel assessment thresholds, access point 302 processes signals from client 304, as client 304 is inside the service area 308. Thus, raising and lowering the start of packet and clear channel assessment thresholds can be used to control cell size.
Figure 4 shows a graph 400 illustrating the relationship between start of packet and clear channel assessment thresholds and client signal strength. As shown, the x-axis, or ordinate, generally indicates time, while the y-axis, or abscissa, indicates signal strength. A
client signal strength is indicated at reference numeral 402. As indicated at reference numeral
9 PCT/US2005/033093 404, if the start of packet and clear channel assessment thresholds are set higher than the client signal strength of client signal 402, therefore the client will be ignored, and packets from the client will not be received and demodulated by the access point, and the access point will transmit regardless of whether the client is transmitting. Conversely, and as indicated at reference numeral 406, if the start of packet and clear channel assessment thresholds are set lower than the client signal strength 402, the client prevents assessment of a clear channel, and the client will not transmit. Furthermore, packets from the client will be received and demodulated by the access point.
Figure 5 shows a graph 500 illustrating the divergence of throughput density with the 1o start of packet and clear channel assessment thresholds are set to the minimum receive sensitivities of the transceivers, as defined by the receivers, and used by the carrier sense multiple access mechanisms within the access points from ideal throughput density as the access point density increases. As shown, the x-axis, or ordinate, generally indicates the number of access points per unit area, while the y-axis, or abscissa, indicates the access point throughput per unit area. More specifically, curve 502 illustrates the throughput density when the start of packet and clear channel assessment thresholds are set to the minimum receive sensitivities of the transceivers and used by the carrier sense multiple access mechanisms within the access points as the access point density increases. It will be appreciated by the skilled artisan that after a certain saturation point 508, adding additional access points without changing cell sizes does not increase throughput. In contrast, line 504 illustrates the ideal throughput density as the access point density increases. In other words, line 504 illustrates the desired increase in throughput as additional access points are added to a wireless network.
Thus, for a given geographic area, there is an ideal upper limit, as indicated at reference numeral 506, on the throughput density, e.g., throughput per unit area.
Furthermore, once the access point density, i.e., the number of access points per unit area, reaches the saturation point, as indicated at reference numeral 508, where the service areas of co-channel access points begin to overlap, as was illustrated in Figure 2, the available throughput density can not be increased further as indicated by curve 502 using prior art methods.
However, if the start of packet threshold and/or the clear channel assessment threshold are raised and/or set in accordance with principles of the present invention, an approximation of the ideal, i.e., throughput density increasing as the access point density increases, line 504, is achieved.
One factor to be taken into consideration as more access points are added to the network or the access point density is increased is the signal-to-interference ratio (SIR). As used herein, the signal-to-interference ratio is the ratio of the intended signal power to the total interference signal power originating from other cells. For example, in a typical 5 wireless local network, the carrier sense multiple access mechanism with start of packet and clear channel assessment thresholds set to the minimum receive sensitivity attempts to ensure there is always adequate signal-to-interference ratio by allowing only one radio to transmit on a particular carrier frequency or channel at a time. However, as was shown in Figure 5, this leads to an upper limit 506 on the achievable throughput density.
Figure 5 shows a graph 500 illustrating the divergence of throughput density with the 1o start of packet and clear channel assessment thresholds are set to the minimum receive sensitivities of the transceivers, as defined by the receivers, and used by the carrier sense multiple access mechanisms within the access points from ideal throughput density as the access point density increases. As shown, the x-axis, or ordinate, generally indicates the number of access points per unit area, while the y-axis, or abscissa, indicates the access point throughput per unit area. More specifically, curve 502 illustrates the throughput density when the start of packet and clear channel assessment thresholds are set to the minimum receive sensitivities of the transceivers and used by the carrier sense multiple access mechanisms within the access points as the access point density increases. It will be appreciated by the skilled artisan that after a certain saturation point 508, adding additional access points without changing cell sizes does not increase throughput. In contrast, line 504 illustrates the ideal throughput density as the access point density increases. In other words, line 504 illustrates the desired increase in throughput as additional access points are added to a wireless network.
Thus, for a given geographic area, there is an ideal upper limit, as indicated at reference numeral 506, on the throughput density, e.g., throughput per unit area.
Furthermore, once the access point density, i.e., the number of access points per unit area, reaches the saturation point, as indicated at reference numeral 508, where the service areas of co-channel access points begin to overlap, as was illustrated in Figure 2, the available throughput density can not be increased further as indicated by curve 502 using prior art methods.
However, if the start of packet threshold and/or the clear channel assessment threshold are raised and/or set in accordance with principles of the present invention, an approximation of the ideal, i.e., throughput density increasing as the access point density increases, line 504, is achieved.
One factor to be taken into consideration as more access points are added to the network or the access point density is increased is the signal-to-interference ratio (SIR). As used herein, the signal-to-interference ratio is the ratio of the intended signal power to the total interference signal power originating from other cells. For example, in a typical 5 wireless local network, the carrier sense multiple access mechanism with start of packet and clear channel assessment thresholds set to the minimum receive sensitivity attempts to ensure there is always adequate signal-to-interference ratio by allowing only one radio to transmit on a particular carrier frequency or channel at a time. However, as was shown in Figure 5, this leads to an upper limit 506 on the achievable throughput density.
10 In contrast, when the carrier sense multiple access mechanisms are all disabled and all of the access points are allowed to transmit without monitoring the activity from other access points, the signal-to-interference ratio depends on the environment that the access points are placed in and the frequency reuse pattern applied thereto. Simulations have demonstrated that there would be adequate signal-to-interference to allow simultaneous and reliable data transfer in multiple co-channel cells, even where all access points transmit simultaneously.
For example, this is especially true for Institute of Electrical and Electronics Engineers 802.11 a where the new frequency allocations provide for in Federal Communications Commissions (FCC) Report and Order 03-287 increases the number of available carrier frequencies or channels from twelve to twenty-three in the United States.
Other simulations, have shown that the signal-to-interference ratio resulting from simultaneous transmissions from all access points in a wireless local area network will likely only restrict data transfers to 36 megabits per second (Mbps) for each access point. Therefore, it has been determined that reducing the service areas of access points in a wireless network to allow simultaneous transmission by co-channel access points is a means of increasing throughput within the network.
One approach to reducing the service area of access points is to reduce the output power of the access points. Although reducing the output power prevents co-channel access points from "hearing" or interfering with one another, reducing the output power also decreases the received signal strength and signal to noise ration within the respective service areas of the access points as will be shown. Moreover, because higher data rates require higher received signal strength than the lower data rates, the usable range of the higher data rates is less than the usable range of the lower data rates as will also be shown.
For example, Figure 6 shows a graphical depiction of access point ranges for various data rates for an access point operated at nominal power. More specifically, Figure 6 shows
For example, this is especially true for Institute of Electrical and Electronics Engineers 802.11 a where the new frequency allocations provide for in Federal Communications Commissions (FCC) Report and Order 03-287 increases the number of available carrier frequencies or channels from twelve to twenty-three in the United States.
Other simulations, have shown that the signal-to-interference ratio resulting from simultaneous transmissions from all access points in a wireless local area network will likely only restrict data transfers to 36 megabits per second (Mbps) for each access point. Therefore, it has been determined that reducing the service areas of access points in a wireless network to allow simultaneous transmission by co-channel access points is a means of increasing throughput within the network.
One approach to reducing the service area of access points is to reduce the output power of the access points. Although reducing the output power prevents co-channel access points from "hearing" or interfering with one another, reducing the output power also decreases the received signal strength and signal to noise ration within the respective service areas of the access points as will be shown. Moreover, because higher data rates require higher received signal strength than the lower data rates, the usable range of the higher data rates is less than the usable range of the lower data rates as will also be shown.
For example, Figure 6 shows a graphical depiction of access point ranges for various data rates for an access point operated at nominal power. More specifically, Figure 6 shows
11 the range of access point 400a for data rates of 54, 24, 12 and 6 Megabits per second, as indicated at reference numerals 604, 606, 608, and 610, respectively. As shown, the 54 Megabit per second range 604 of access point 600a extends just beyond an intended service area, indicated at reference numera1602a. Similarly, the 24 Megabit per second range 606 extends beyond the 54 Megabit per second range 604. Extending beyond the 54 and 24 Megabit per second ranges 604, 606, the 12 and 6 Megabit per second ranges 608, 610 encompasses part or all of the intended coverage area 602b of access point 600b.
Figure 7 shows a graphical depiction of controlling cell size by reducing output power, i.e., decreasing the output power of two co-channel access points 700a, 700b from their nominal output powers. Data rates of 54, 24, 12 and 6 Megabits per second are again used for example. Data rates of 54, 24, 12 and 6 Megabits per second, are indicated at reference numerals 704a, 706a, 708a, and 710a for access point 700a and 704b, 706b, 708b, and 710b for access points 700b, respectively. More specifically, the output powers of the access points are reduced such that the 6 Megabit per second ranges 710a, 710b do not extend beyond the intended service area as indicated at reference numerals 702a, 702b, respectively.
Thus, the two co-channel access points 702a, 702b can transmit simultaneously without interfering with each other, thereby increasing throughput. However, as will be appreciated by those of ordinary skill in the art, the useable data rate within each intended service area 702a, 702b has been significantly reduced. For example, a data rate of 54 Megabits per second 704a, 704b is not available throughout much of the intended service areas 702a, 702b.
Therefore, controlling cell size by reducing output power results in limited throughput as there are generally breaches in the total coverage area for the higher data rates as generally indicated by reference numeral 712.
In contrast, the present invention controls cell size in a way that allows multiple access points or cells on the same carrier frequency to transmit simultaneously, but without reducing the transmit or output power, thereby preserving the range capability of the higher data rates. More specifically, and for example, Figure 8 shows a graphical depiction of controlling cell size by increasing or decreasing and/or setting the start of packet threshold and/or the clear channel assessment threshold in accordance with principles of the present invention.
By changing the start of packet threshold and/or the clear channel assessment threshold rather than changing the transmit power, the range of the lower data rates is restricted without shrinking the coverage area of the higher data rates.
Figure 8 shows the results of raising the start of packet and clear channel assessment thresholds such that access
Figure 7 shows a graphical depiction of controlling cell size by reducing output power, i.e., decreasing the output power of two co-channel access points 700a, 700b from their nominal output powers. Data rates of 54, 24, 12 and 6 Megabits per second are again used for example. Data rates of 54, 24, 12 and 6 Megabits per second, are indicated at reference numerals 704a, 706a, 708a, and 710a for access point 700a and 704b, 706b, 708b, and 710b for access points 700b, respectively. More specifically, the output powers of the access points are reduced such that the 6 Megabit per second ranges 710a, 710b do not extend beyond the intended service area as indicated at reference numerals 702a, 702b, respectively.
Thus, the two co-channel access points 702a, 702b can transmit simultaneously without interfering with each other, thereby increasing throughput. However, as will be appreciated by those of ordinary skill in the art, the useable data rate within each intended service area 702a, 702b has been significantly reduced. For example, a data rate of 54 Megabits per second 704a, 704b is not available throughout much of the intended service areas 702a, 702b.
Therefore, controlling cell size by reducing output power results in limited throughput as there are generally breaches in the total coverage area for the higher data rates as generally indicated by reference numeral 712.
In contrast, the present invention controls cell size in a way that allows multiple access points or cells on the same carrier frequency to transmit simultaneously, but without reducing the transmit or output power, thereby preserving the range capability of the higher data rates. More specifically, and for example, Figure 8 shows a graphical depiction of controlling cell size by increasing or decreasing and/or setting the start of packet threshold and/or the clear channel assessment threshold in accordance with principles of the present invention.
By changing the start of packet threshold and/or the clear channel assessment threshold rather than changing the transmit power, the range of the lower data rates is restricted without shrinking the coverage area of the higher data rates.
Figure 8 shows the results of raising the start of packet and clear channel assessment thresholds such that access
12 points 800a, 800b 54 Megabit per second ranges 804a, 804b extend just to the edge of the desired service areas 802a, 802b, respectively. Thus, the two access points 800a, 800b can now transmit simultaneously without reduced transmit power and, consequently, not be penalized with reduced received signal strength within the desired service areas 802a, 802b.
Thus, referring once again to Figure 1, in a wireless network 100 in accordance with principles of the present invention, access point 102a-n output power is not an exclusive factor in setting the service area or cell size. Rather, a combination of the output power, the start of packet threshold, and/or the clear channel assessment threshold is set to determine the service areas of access points 102a-n. Moreover, and in accordance with one aspect of the present invention, by fixing the start of packet and clear channel assessment thresholds relative to the output power, changing the output power does not change the service area, so long as the output power is maintained above some minimum level that prevents an inadequate received signal level at a client 104a-m within the service area.
In addition, a wireless network 100 in accordance with principles of the present invention eliminates the upper limit 506 on the achievable throughput density was described in conjunction with Figure 5. Thus, by reducing the service area per access point while increasing access point density without degrading the signal strength at client with the wireless network 100, continuously increasing throughput density with increasing access point density is provided, along with a minimum throughput per access point.
By virtue of the foregoing, there is thus provided a system and method for a high density wireless local area network that controls cell size in a way that allows multiple cells on the same carrier frequency to transmit simultaneously, but without reducing the transmit power, thereby preserving the range capability of the higher data rates.
While the present system has been illustrated by the description of embodiments thereof, and while the embodiments have been described in considerable detail, it is not the intention of the applicants to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications will readily appear to those skilled in the art. It will be understood that the present invention is applicable to any contention based open medium network. Moreover, such a network is not limited to operation in any particular frequency band; but rather, may operate at any frequency as desired. Further, the invention is not limited to operation in accordance with any standard or regulations.
Therefore, the invention, in its broader aspects, is not limited to the specific details, the representative apparatus, and illustrative examples shown and described. Accordingly, departures may be
Thus, referring once again to Figure 1, in a wireless network 100 in accordance with principles of the present invention, access point 102a-n output power is not an exclusive factor in setting the service area or cell size. Rather, a combination of the output power, the start of packet threshold, and/or the clear channel assessment threshold is set to determine the service areas of access points 102a-n. Moreover, and in accordance with one aspect of the present invention, by fixing the start of packet and clear channel assessment thresholds relative to the output power, changing the output power does not change the service area, so long as the output power is maintained above some minimum level that prevents an inadequate received signal level at a client 104a-m within the service area.
In addition, a wireless network 100 in accordance with principles of the present invention eliminates the upper limit 506 on the achievable throughput density was described in conjunction with Figure 5. Thus, by reducing the service area per access point while increasing access point density without degrading the signal strength at client with the wireless network 100, continuously increasing throughput density with increasing access point density is provided, along with a minimum throughput per access point.
By virtue of the foregoing, there is thus provided a system and method for a high density wireless local area network that controls cell size in a way that allows multiple cells on the same carrier frequency to transmit simultaneously, but without reducing the transmit power, thereby preserving the range capability of the higher data rates.
While the present system has been illustrated by the description of embodiments thereof, and while the embodiments have been described in considerable detail, it is not the intention of the applicants to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications will readily appear to those skilled in the art. It will be understood that the present invention is applicable to any contention based open medium network. Moreover, such a network is not limited to operation in any particular frequency band; but rather, may operate at any frequency as desired. Further, the invention is not limited to operation in accordance with any standard or regulations.
Therefore, the invention, in its broader aspects, is not limited to the specific details, the representative apparatus, and illustrative examples shown and described. Accordingly, departures may be
13 made from such details without departing from the spirit or scope of the applicants' general inventive concept.
Claims (27)
1. A method for controlling cell size associated with an access point having a receive sensitivity and an output power, comprising:
changing at least one of a start of packet threshold and a clear channel assessment threshold to vary the cell size of the access point;
tracking a change in output power with the start of packet threshold and the clear channel assessment threshold; wherein a range of a lower data rate is restricted without shrinking the coverage area of a higher data rate; and wherein changing the output power does not change the cell size, so long as the output power is maintained above a minimum level that prevents an inadequate received signal level at a client within the cell.
changing at least one of a start of packet threshold and a clear channel assessment threshold to vary the cell size of the access point;
tracking a change in output power with the start of packet threshold and the clear channel assessment threshold; wherein a range of a lower data rate is restricted without shrinking the coverage area of a higher data rate; and wherein changing the output power does not change the cell size, so long as the output power is maintained above a minimum level that prevents an inadequate received signal level at a client within the cell.
2. The method for controlling cell size associated with an access point of claim 1, wherein the output power of the access point is maintained.
3. The method for controlling cell size associated with an access point of claim 1, wherein at least one of a start of packet threshold and a clear channel assessment threshold are changed relative to the output power.
4. The method for controlling cell size associated with an access point of claim 1, further comprising raising at least one of the start of packet threshold and the clear channel assessment threshold above the minimum receive sensitivity of the access point.
5. The method for controlling cell size associated with an access point of claim 1, further comprising increasing cell size by decreasing at least one of the start of packet threshold and the clear channel assessment threshold.
6. The method for controlling cell size associated with an access point of claim 1, further comprising decreasing cell size by increasing at least one of the start of packet threshold and the clear channel assessment threshold.
7. The method for controlling cell size associated with an access point of claim 1, wherein the access point is assigned to the same carrier frequency as another access point.
8. A method for operating a high density wireless local area network, comprising:
assigning multiple access points having receive sensitivities and output powers to the same carrier frequency;
controlling cell sizes associated with the access points by changing at least one of a start of packet threshold and a clear channel assessment threshold to vary the cell sizes of the access points;
tracking changes in output powers with the start of packet threshold and the clear channel assessment threshold; wherein a range of a lower data rate is restricted without shrinking the coverage area of a higher data rate; and wherein changing the output powers does not change the cell sizes, so long as the output powers are maintained above a minimum level that prevents an inadequate received signal level at a client within the cells.
assigning multiple access points having receive sensitivities and output powers to the same carrier frequency;
controlling cell sizes associated with the access points by changing at least one of a start of packet threshold and a clear channel assessment threshold to vary the cell sizes of the access points;
tracking changes in output powers with the start of packet threshold and the clear channel assessment threshold; wherein a range of a lower data rate is restricted without shrinking the coverage area of a higher data rate; and wherein changing the output powers does not change the cell sizes, so long as the output powers are maintained above a minimum level that prevents an inadequate received signal level at a client within the cells.
9. The method for operating a high density wireless local area network of claim 8, wherein the output powers of the access points are maintained.
10. The method for operating a high density wireless local area network of claim 8, wherein at least one of the start of packet threshold and the clear channel assessment threshold are changed relative to the output powers.
11. The method for operating a high density wireless local area network of claim 8, further comprising raising at least one of the start of packet threshold and the clear channel assessment threshold above the minimum receive sensitivities of the access points.
12. The method for operating a high density wireless local area network of claim 8, further comprising increasing cell sizes by decreasing at least one of the start of packet threshold and the clear channel assessment threshold.
13. The method for operating a high density wireless local area network of claim 8, further comprising decreasing cell sizes by increasing at least one of the start of packet threshold and the clear channel assessment threshold.
14. An access point, comprising:
a transceiver configured for engaging in wireless communications with clients, and including a transmitter having an output power and a receiver having a receive sensitivity; and a controller coupled to the transceiver and configured to control the operation of the transceiver when engaging in wireless communications with the clients, and including a processor configured for executing program code and a memory configured for storing the program code and at least one a start of packet threshold and a clear channel assessment threshold;
wherein at least one of the start of packet threshold and the clear channel assessment threshold is varied to control the cell size of the access point;
wherein a range of a lower data rate is restricted without shrinking the coverage area of a higher data rate;
wherein the start of packet threshold and the clear channel assessment threshold track a change in output power; and wherein changing the output power does not change the cell size, so long as the output power is maintained above a minimum level that prevents an inadequate received signal level at a client within the cell.
a transceiver configured for engaging in wireless communications with clients, and including a transmitter having an output power and a receiver having a receive sensitivity; and a controller coupled to the transceiver and configured to control the operation of the transceiver when engaging in wireless communications with the clients, and including a processor configured for executing program code and a memory configured for storing the program code and at least one a start of packet threshold and a clear channel assessment threshold;
wherein at least one of the start of packet threshold and the clear channel assessment threshold is varied to control the cell size of the access point;
wherein a range of a lower data rate is restricted without shrinking the coverage area of a higher data rate;
wherein the start of packet threshold and the clear channel assessment threshold track a change in output power; and wherein changing the output power does not change the cell size, so long as the output power is maintained above a minimum level that prevents an inadequate received signal level at a client within the cell.
15. The access point of claim 14, wherein the output power of the transmitter is maintained.
16. The access point of claim 14, wherein at least one of a start of packet threshold and a clear channel assessment threshold are changed relative to the output power.
17. The access point of claim 14, wherein at least one of the start of packet threshold and the clear channel assessment threshold is raised above the minimum receive sensitivity of the access point.
18. The access point of claim 14, wherein the cell size is increased by decreasing at least one of the start of packet threshold and the clear channel assessment threshold.
19. The access point of claim 14, wherein the cell size is decreased by increasing at least one of the start of packet threshold and the clear channel assessment threshold.
20. The access point of claim 14, wherein the access point is assigned to the same carrier frequency as another access point.
21. A high density wireless local area network, comprising:
a first access point including a first transmitter having an output power, a first receiver having a receive sensitivity, a first processor configured for executing program code to control the operation of the first transmitter and the first receiver when engaging in wireless communications with clients, and a first memory configured for storing the program code and at least one of a start of packet threshold and a clear channel assessment threshold;
a second access point including a second transmitter having an output power, a second receiver having a receive sensitivity, a second processor configured for executing program code to control the operation of the second transmitter and the second receiver when engaging in wireless communications with clients, and a second memory configured for storing the program code and at least one of a start of packet threshold and a clear channel assessment threshold;
wherein the first and second access points are assigned the same carrier frequency; and wherein cell sizes associated with the first and second access points are controlled by changing at least one of the start of packet thresholds and the clear channel assessment thresholds to vary the cells sizes of the access points;
wherein a range of a lower data rate is restricted without shrinking the coverage area of a higher data rate;
wherein the start of packet and clear channel assessment thresholds track changes in output powers; and wherein changing the output powers does not change the cell sizes, so long as the output powers are maintained above a minimum level that prevents an inadequate received signal level at a client within the cells.
a first access point including a first transmitter having an output power, a first receiver having a receive sensitivity, a first processor configured for executing program code to control the operation of the first transmitter and the first receiver when engaging in wireless communications with clients, and a first memory configured for storing the program code and at least one of a start of packet threshold and a clear channel assessment threshold;
a second access point including a second transmitter having an output power, a second receiver having a receive sensitivity, a second processor configured for executing program code to control the operation of the second transmitter and the second receiver when engaging in wireless communications with clients, and a second memory configured for storing the program code and at least one of a start of packet threshold and a clear channel assessment threshold;
wherein the first and second access points are assigned the same carrier frequency; and wherein cell sizes associated with the first and second access points are controlled by changing at least one of the start of packet thresholds and the clear channel assessment thresholds to vary the cells sizes of the access points;
wherein a range of a lower data rate is restricted without shrinking the coverage area of a higher data rate;
wherein the start of packet and clear channel assessment thresholds track changes in output powers; and wherein changing the output powers does not change the cell sizes, so long as the output powers are maintained above a minimum level that prevents an inadequate received signal level at a client within the cells.
22. The high density wireless local area network of claim 21, wherein the output powers of the first and second transmitters are maintained.
23. The high density wireless local area network of claim 21, wherein at least one of the start of packet thresholds and the clear channel assessment thresholds are changed relative to the output powers.
24. The high density wireless local area network of claim 21, wherein at the least one of the start of packet thresholds and clear channel assessment thresholds are raised above the minimum receive sensitivities of the first and second receivers.
25. The high density wireless local area network of claim 21, wherein the cell sizes are increased by decreasing at the least one of the start of packet thresholds and clear channel assessment thresholds.
26. The high density wireless local area network of claim 21, wherein the cell sizes are decreased by increasing at the least one of the start of packet thresholds and clear channel assessment thresholds.
27. A computer-readable medium having stored thereon instructions for controlling cell size associated with an access point having a receive sensitivity and an output power, the instructions when executed by a processor cause the processor to implement the method of any one of claims 1 to 13.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US10/977,284 US7529218B2 (en) | 2004-08-25 | 2004-10-29 | High density WLAN system |
| US10/977,284 | 2004-10-29 | ||
| PCT/US2005/033093 WO2006049709A2 (en) | 2004-10-29 | 2005-09-14 | High density wlan system |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2582395A1 CA2582395A1 (en) | 2006-05-11 |
| CA2582395C true CA2582395C (en) | 2012-10-30 |
Family
ID=36261742
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA2582395A Active CA2582395C (en) | 2004-10-29 | 2005-09-14 | High density wlan system |
Country Status (5)
| Country | Link |
|---|---|
| US (1) | US7529218B2 (en) |
| EP (1) | EP1806010B1 (en) |
| CN (1) | CN101023688B (en) |
| CA (1) | CA2582395C (en) |
| WO (1) | WO2006049709A2 (en) |
Families Citing this family (60)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20070060155A1 (en) * | 2005-08-31 | 2007-03-15 | Emanuel Kahana | System and method to dynamically adapt a CCA threshold |
| KR20090042846A (en) * | 2006-09-20 | 2009-04-30 | 닛본 덴끼 가부시끼가이샤 | Carrier assignment method for cellular system, cellular system, base station, and mobile ststion |
| US20080320108A1 (en) * | 2007-06-20 | 2008-12-25 | Microsoft Corporation | Management Policies For Dense Wireless Access Point Infrastructures in Wireless Local Area Networks |
| US7907562B2 (en) * | 2007-06-20 | 2011-03-15 | Microsoft Corporation | Managing dense wireless access point infrastructures in wireless local area networks |
| KR101386066B1 (en) | 2007-09-10 | 2014-04-17 | 삼성전자주식회사 | Method of controlling cell coverage and system of enabling the method |
| CN101594346B (en) * | 2008-05-28 | 2011-12-07 | 北京中电华大电子设计有限责任公司 | Clear channel assessment procedure for 802.11n device |
| US10368318B2 (en) * | 2010-12-30 | 2019-07-30 | Telefonaktiebolaget Lm Ericsson (Publ) | Wireless operation in very high density environments |
| US8649458B2 (en) | 2012-05-29 | 2014-02-11 | Magnolia Broadband Inc. | Using antenna pooling to enhance a MIMO receiver augmented by RF beamforming |
| US8644413B2 (en) | 2012-05-29 | 2014-02-04 | Magnolia Broadband Inc. | Implementing blind tuning in hybrid MIMO RF beamforming systems |
| US8971452B2 (en) | 2012-05-29 | 2015-03-03 | Magnolia Broadband Inc. | Using 3G/4G baseband signals for tuning beamformers in hybrid MIMO RDN systems |
| US8767862B2 (en) | 2012-05-29 | 2014-07-01 | Magnolia Broadband Inc. | Beamformer phase optimization for a multi-layer MIMO system augmented by radio distribution network |
| US8885757B2 (en) | 2012-05-29 | 2014-11-11 | Magnolia Broadband Inc. | Calibration of MIMO systems with radio distribution networks |
| US9154204B2 (en) | 2012-06-11 | 2015-10-06 | Magnolia Broadband Inc. | Implementing transmit RDN architectures in uplink MIMO systems |
| CN102769912B (en) * | 2012-07-16 | 2015-01-21 | 北京星网锐捷网络技术有限公司 | Message transmission method and device applied to WLAN (Wireless Local Area Network) as well as network equipment |
| US8934369B2 (en) | 2012-10-05 | 2015-01-13 | Cisco Technology, Inc. | Direction aware neighbor list infrastructure assisted roaming |
| US9319191B2 (en) * | 2013-01-14 | 2016-04-19 | Qualcomm Incorporated | System and method for selecting medium access parameters for each communication session |
| US9343808B2 (en) | 2013-02-08 | 2016-05-17 | Magnotod Llc | Multi-beam MIMO time division duplex base station using subset of radios |
| US8797969B1 (en) | 2013-02-08 | 2014-08-05 | Magnolia Broadband Inc. | Implementing multi user multiple input multiple output (MU MIMO) base station using single-user (SU) MIMO co-located base stations |
| US20140226740A1 (en) | 2013-02-13 | 2014-08-14 | Magnolia Broadband Inc. | Multi-beam co-channel wi-fi access point |
| US8989103B2 (en) | 2013-02-13 | 2015-03-24 | Magnolia Broadband Inc. | Method and system for selective attenuation of preamble reception in co-located WI FI access points |
| US9155110B2 (en) | 2013-03-27 | 2015-10-06 | Magnolia Broadband Inc. | System and method for co-located and co-channel Wi-Fi access points |
| US9204451B2 (en) * | 2013-03-06 | 2015-12-01 | Broadcom Corporation | Clear channel assessment (CCA) levels within wireless communications |
| US9100968B2 (en) | 2013-05-09 | 2015-08-04 | Magnolia Broadband Inc. | Method and system for digital cancellation scheme with multi-beam |
| US9883404B2 (en) * | 2013-06-11 | 2018-01-30 | Qualcomm Incorporated | LTE/LTE—A uplink carrier aggregation using unlicensed spectrum |
| US9425882B2 (en) | 2013-06-28 | 2016-08-23 | Magnolia Broadband Inc. | Wi-Fi radio distribution network stations and method of operating Wi-Fi RDN stations |
| US8995416B2 (en) * | 2013-07-10 | 2015-03-31 | Magnolia Broadband Inc. | System and method for simultaneous co-channel access of neighboring access points |
| CN104333858B (en) * | 2013-07-22 | 2018-03-16 | 中国科学院信息工程研究所 | It is a kind of based on the channel resource control method for going association/de-authentication frames |
| US9497781B2 (en) | 2013-08-13 | 2016-11-15 | Magnolia Broadband Inc. | System and method for co-located and co-channel Wi-Fi access points |
| US9060362B2 (en) * | 2013-09-12 | 2015-06-16 | Magnolia Broadband Inc. | Method and system for accessing an occupied Wi-Fi channel by a client using a nulling scheme |
| US9088898B2 (en) | 2013-09-12 | 2015-07-21 | Magnolia Broadband Inc. | System and method for cooperative scheduling for co-located access points |
| US9172454B2 (en) | 2013-11-01 | 2015-10-27 | Magnolia Broadband Inc. | Method and system for calibrating a transceiver array |
| US8891598B1 (en) | 2013-11-19 | 2014-11-18 | Magnolia Broadband Inc. | Transmitter and receiver calibration for obtaining the channel reciprocity for time division duplex MIMO systems |
| US8929322B1 (en) | 2013-11-20 | 2015-01-06 | Magnolia Broadband Inc. | System and method for side lobe suppression using controlled signal cancellation |
| US8942134B1 (en) | 2013-11-20 | 2015-01-27 | Magnolia Broadband Inc. | System and method for selective registration in a multi-beam system |
| US9294177B2 (en) | 2013-11-26 | 2016-03-22 | Magnolia Broadband Inc. | System and method for transmit and receive antenna patterns calibration for time division duplex (TDD) systems |
| US9014066B1 (en) | 2013-11-26 | 2015-04-21 | Magnolia Broadband Inc. | System and method for transmit and receive antenna patterns calibration for time division duplex (TDD) systems |
| US9042276B1 (en) | 2013-12-05 | 2015-05-26 | Magnolia Broadband Inc. | Multiple co-located multi-user-MIMO access points |
| CN103731169A (en) * | 2013-12-06 | 2014-04-16 | 南京智达康无线通信科技股份有限公司 | Receiving sensitivity improvement method |
| US9521587B2 (en) * | 2013-12-11 | 2016-12-13 | Futurewei Technologies, Inc. | System and method for determining a clear channel assessment threshold |
| US10104565B2 (en) | 2013-12-13 | 2018-10-16 | Qualcomm Incorporated | CSI feedback in LTE/LTE-advanced systems with unlicensed spectrum |
| US9172446B2 (en) | 2014-03-19 | 2015-10-27 | Magnolia Broadband Inc. | Method and system for supporting sparse explicit sounding by implicit data |
| US9100154B1 (en) | 2014-03-19 | 2015-08-04 | Magnolia Broadband Inc. | Method and system for explicit AP-to-AP sounding in an 802.11 network |
| US9271176B2 (en) | 2014-03-28 | 2016-02-23 | Magnolia Broadband Inc. | System and method for backhaul based sounding feedback |
| US9578657B2 (en) * | 2014-04-11 | 2017-02-21 | Realtek Semiconductor Corporation | Wireless communication method and device |
| US9219986B2 (en) | 2014-04-22 | 2015-12-22 | Cisco Technology, Inc. | Client device location using synchronized wireless receivers |
| WO2015163803A1 (en) * | 2014-04-25 | 2015-10-29 | Telefonaktiebolaget L M Ericsson (Publ) | Method and apparatus relating to threshold control in wireless communications |
| US20150319787A1 (en) * | 2014-04-30 | 2015-11-05 | Alcatel-Lucent Usa Inc. | Selectively decoding packet payloads based on decoded packet headers |
| US10251198B2 (en) * | 2014-06-26 | 2019-04-02 | Telefonaktiebolaget Lm Ericsson (Publ) | Clear channel assessment threshold configuration |
| EP3162156B1 (en) * | 2014-06-27 | 2020-04-22 | Techflux Inc. | Method and device for transmitting data unit |
| EP3167681B1 (en) * | 2014-08-12 | 2019-05-22 | MediaTek Inc. | Method to improve channel access opportunity in a wireless communications system |
| US10045302B2 (en) * | 2014-09-16 | 2018-08-07 | Qualcomm Incorporated | Power control in wireless networks |
| US10064066B2 (en) * | 2014-10-20 | 2018-08-28 | Lg Electronics Inc. | Method for transmitting and receiving wireless signal in wireless communication system and apparatus therefor |
| US20160183196A1 (en) * | 2014-12-17 | 2016-06-23 | Comcast Cable Communications, Llc | Methods for dynamically adjusting range of a wireless signal |
| US20160212767A1 (en) * | 2015-01-16 | 2016-07-21 | Sharp Laboratories Of America, Inc. | Systems and methods for contention access in license assisted access |
| US9622266B2 (en) * | 2015-02-20 | 2017-04-11 | Nokia Technologies Oy | Configuring simultaneous transmissions in wireless network |
| CN106060835B (en) * | 2016-05-05 | 2019-07-19 | 锐捷网络股份有限公司 | A kind of WLAN anti-disturbance method and wireless lan controller |
| US10306487B1 (en) | 2016-06-23 | 2019-05-28 | CSC Holdings, LLC | Operational parameter allocation in a wireless access point |
| US10251123B2 (en) | 2017-07-09 | 2019-04-02 | Cisco Technology, Inc. | Receiver start of packet optimization for wireless networks |
| CN108718453B (en) * | 2018-06-15 | 2022-03-25 | 合肥工业大学 | Regional networking method under high-density WLAN scene |
| CN112118638B (en) * | 2019-06-19 | 2022-10-28 | 瑞昱半导体股份有限公司 | Idle channel evaluation scheme decision method and communication system thereof |
Family Cites Families (20)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB8927636D0 (en) * | 1989-12-06 | 1990-02-07 | Purification Prod | Improvements in the production of particulate solid-bearing air-permeable sheet materials |
| US5241685A (en) * | 1991-03-15 | 1993-08-31 | Telefonaktiebolaget L M Ericsson | Load sharing control for a mobile cellular radio system |
| CA2129193C (en) * | 1994-07-29 | 1999-07-20 | Peter E. Reissner | Access point tracking for mobile wireless network node |
| US6052408A (en) * | 1995-09-06 | 2000-04-18 | Aironet Wireless Communications, Inc. | Cellular communication system with dynamically modified data transmission parameters |
| SE515588C2 (en) * | 1996-01-25 | 2001-09-03 | Ericsson Telefon Ab L M | Mini cells with variable for size of payload in a mobile phone network |
| US5946631A (en) * | 1996-10-17 | 1999-08-31 | Philips Electronics North America Corporation | Real-time CSMA method having the capability to adaptively vary cell sizes and a wireless network for implementing the same |
| US6067291A (en) * | 1997-09-23 | 2000-05-23 | Lucent Technologies Inc. | Wireless local area network with enhanced carrier sense provision |
| US6438379B1 (en) * | 1999-05-28 | 2002-08-20 | Lucent Technologies, Inc. | Power control and cell site location technique for CDMA systems with hierarchical architecture |
| EP1139606A1 (en) | 2000-03-28 | 2001-10-04 | Lucent Technologies Inc. | Wireless communication in a lan with varying signal level thresholds |
| CA2323164A1 (en) * | 2000-10-11 | 2002-04-11 | Ramesh Mantha | Method, system and apparatus for improving reception in multiple access communication systems |
| US7206840B2 (en) * | 2001-05-11 | 2007-04-17 | Koninklike Philips Electronics N.V. | Dynamic frequency selection scheme for IEEE 802.11 WLANs |
| US6851027B2 (en) * | 2001-09-17 | 2005-02-01 | Intel Corporation | Memory system organized into blocks of different sizes and allocation method therefor |
| US7272358B2 (en) * | 2002-03-07 | 2007-09-18 | Texas Instruments Incorporated | Channelization scheme for wireless local area networks |
| US7408907B2 (en) * | 2002-09-11 | 2008-08-05 | Cisco Technology, Inc. | System and method for management of a shared frequency band using client-specific management techniques |
| US8412106B2 (en) * | 2002-11-04 | 2013-04-02 | Xr Communications, Llc | Directed wireless communication |
| US7020438B2 (en) * | 2003-01-09 | 2006-03-28 | Nokia Corporation | Selection of access point in a wireless communication system |
| US7167708B2 (en) * | 2003-02-24 | 2007-01-23 | Autocell Laboratories Inc. | Wireless channel selection apparatus including scanning logic |
| CN1567869B (en) * | 2003-06-30 | 2010-05-05 | 叶启祥 | Interference control method capable of avoiding interference damage and increasing space reuse rate |
| US7079494B2 (en) * | 2004-01-08 | 2006-07-18 | Interdigital Technology Corporation | Wireless communication method and apparatus for determining the minimum power level of access point transmissions |
| US7526308B2 (en) * | 2005-04-28 | 2009-04-28 | Intel Corporation | Adaptive control physical carrier sense parameters in wireless networks |
-
2004
- 2004-10-29 US US10/977,284 patent/US7529218B2/en active Active
-
2005
- 2005-09-14 CN CN2005800312233A patent/CN101023688B/en active Active
- 2005-09-14 CA CA2582395A patent/CA2582395C/en active Active
- 2005-09-14 WO PCT/US2005/033093 patent/WO2006049709A2/en active Application Filing
- 2005-09-14 EP EP05798436.1A patent/EP1806010B1/en active Active
Also Published As
| Publication number | Publication date |
|---|---|
| WO2006049709A2 (en) | 2006-05-11 |
| EP1806010A2 (en) | 2007-07-11 |
| US20060092889A1 (en) | 2006-05-04 |
| WO2006049709A3 (en) | 2006-07-27 |
| EP1806010B1 (en) | 2013-06-19 |
| US7529218B2 (en) | 2009-05-05 |
| CN101023688B (en) | 2010-11-03 |
| EP1806010A4 (en) | 2011-11-30 |
| CN101023688A (en) | 2007-08-22 |
| CA2582395A1 (en) | 2006-05-11 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CA2582395C (en) | High density wlan system | |
| JP4654245B2 (en) | System and method utilizing cognitive transceiver for ad hoc networking | |
| US9497700B2 (en) | Dynamic channel selection algorithms for interference management in Wi-Fi networks | |
| US8588115B2 (en) | Apparatus for controlling channel switching in wireless networks | |
| US8005480B2 (en) | Communication initialization method at medium access control layer in a cognitive radio wireless communication system | |
| JP4413934B2 (en) | Wireless communication apparatus and wireless communication method | |
| JP5048062B2 (en) | Beacon transmission / reception method and system | |
| JP5848383B2 (en) | Wireless communication scheme and WLAN for signaling delay management messages | |
| Shu et al. | WLC05-3: Medium access control for multi-channel parallel transmission in cognitive radio networks | |
| JP2008524902A (en) | Method and apparatus for reducing mutual interference of network subscribers in a wireless network | |
| JP5283443B2 (en) | Composite communication system, prohibition signal transmission apparatus, radio base station, and method | |
| US7813738B2 (en) | WLAN operating on multiple adjacent bands | |
| US20030081654A1 (en) | Dynamic frequency-hopping system | |
| US20120163314A1 (en) | Method and apparatus of sending frames in cognitive radio system | |
| Fujii et al. | Spectrum sharing by adaptive transmit power control for low priority systems and achievable capacity | |
| KR20020063299A (en) | Dynamic Frequency-Hoping System | |
| Lopez-Perez et al. | Adaptive energy threshold for improved co-existence between licensed assisted access and Wi-Fi |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request |