US 20060092910 A1
A radio frequency communications system (100) includes wireless terminals (102) and base sites (104). The wireless terminals communicate with the base sites over a radio frequency channel (106). The base sites are interconnected to each other and other network elements via a packet network. The communication system has a radio frequency channel (400) with time slots (406, 408) for transmission of both delay-sensitive data, such as streaming audio and video, and non-delay-sensitive data. A method and apparatus are provided for determining whether a time slot in the radio frequency channel is to be allocated to delay-sensitive data or non-delay-sensitive data (704, 706, 708). Each packet of data transmitted over the wireless channel has a type of service field (900). The type of service field has a precedence or priority value (902) and a service type (904). The priority values are used to determine which packet should be transmitted across the radio frequency channel next and the service type determines the transmission protocol.
11. In a wireless communications system where packets of data are transmitted over a wireless channel, a method for determining which packet of a plurality of packets should be transmitted next over the wireless channel, the method comprising the steps of:
determining a precedence value for each packet to be transmitted over the wireless channel;
selecting a packet to be transmitted next over the wireless channel based on the precedence value, wherein the precedence value for each packet is determined based on whether the each packet includes data to set up communications over the wireless channel.
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29. In a wireless communications system where packets of data are transmitted over a wireless channel, an apparatus for determining which packet of a plurality of packets should be transmitted next over the wireless channel, the apparatus comprising:
a processor that:
determines a precedence value for each packet to be transmitted over the wireless channel; and
a wireless modem coupled to the processor that:
selects a packet to be transmitted next over the wireless channel based on the precedence value, wherein the precedence value for each packet is determined based on whether the each packet includes data to set up communications over the wireless channel.
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33. The method of
The invention generally relates to communications systems, and in particular, to a method and apparatus for organizing and scheduling multimedia data transfers over a wireless channel in order to support delay-sensitive, streaming data, such as audio and video data, and non-delay-sensitive data, such as Web pages.
Wireless data communication systems for transmitting multimedia data, including audio, video and other data, are known. Recently, the explosion in the use of the Internet has dramatically increased multimedia data communication needs, including wireless data communication needs. Internet communications follow a packet-based protocol with wide variance in the size and frequency of packets. Generation of Internet packets generally occurs without regard to the actual physical networks that will carry the data. While this packet-based communication has great advantages, it presents numerous challenges for the efficient transmission of data over a particular physical network.
Known wireless data communication systems that support Internet access are typically a “retrofit” of Internet packets on top of an existing physical network. Unfortunately, these retrofits do not typically efficiently use bandwidth. And, performance is either sacrificed or uncontrolled, where performance includes parameters such as delay and jitter. Most existing systems over engineer the available bandwidth to accommodate a predefined maximum amount of traffic. Although this may be acceptable in wired networks, the limitations on wireless networks do not permit such a luxury. While all wireless packetized data presents some challenge, packetized audio and video streaming data is particularly challenging since the performance, namely, delay and jitter, may inhibit effective communications, in particular in the case of a two-way conversation.
Therefore, a need exists for a new paradigm in the communication of multimedia data over a wireless channel.
Briefly, in a wireless communication system having a wireless channel with time slots for transmission of both delay-sensitive data and non-delay-sensitive data, a method and apparatus are provided for determining whether a time slot in the wireless channel is to be allocated to delay-sensitive data or non-delay-sensitive data. First an ideal slot separation is determined for each delay-sensitive application using the wireless channel. Then, for each delay-sensitive application, a number of time slots since a time slot was granted to the delay-sensitive application is calculated. The number of slots since a time slot was last granted is compared with the ideal slot separation for the delay-sensitive application. A delay-sensitive time slot is allocated if a delay-sensitive application has the number of slots since a time slot was granted equal to or greater than the ideal slot separation for that delay-sensitive application. The delay-sensitive data time slot is granted to the delay-sensitive application that has its number of slots since a slot was granted the most above the ideal slot separation. That is, the delay-sensitive application that has waited the longest beyond its ideal slot separation is granted the delay-sensitive time slot on the wireless channel. Delay-sensitive time slots are granted on the wireless channel until there are no delay-sensitive applications at or beyond their ideal slot separation, meaning no delay-sensitive slot should be granted.
When no delay-sensitive slots are needed, non-delay-sensitive data slots are granted. Preferably there are non-delay-sensitive slots for acknowledgements, random access and nonspecific non-delay-sensitive data. After a determination that there are no delay-sensitive slots needed, a determination is made as to whether any acknowledgement slots are needed. Acknowledgement slots are provided in the wireless channel to acknowledge transmitted packets. If no acknowledgement slots are currently needed in the wireless channel, then a determination is made as to whether any nonspecific non-delay-sensitive data slots are needed. If needed, nonspecific non-delay-sensitive data slots are granted on the wireless channel unless a maximum time period between random access slots has occurred. Random access slots are the means by which wireless terminals request channel resources, i.e., delay-sensitive slots and non-delay-sensitive slots. Therefore, random access slots must be provided periodically to guarantee access to the wireless channel.
Each packet has a precedence or priority value and a service type. The priority values are used to determine among multiple packets waiting for transfer, the packet that should be transmitted next. Where multiple packets are suitable for a particular transmission, packets with the highest priority values are transmitted first. The service types are used to determine an error protocol and a channel access method for the packet. The priority values are set based on the content of the packet. For example, emergency data may be given priority over non-emergency data of the same type. Delay-sensitive data, such as audio and video data, may be given priority over non-delay-sensitive data. A default value of priority is provided for backward compatibility with software and systems not using priority values. Preferably, five service types are defined corresponding to the five service types used in an Internet protocol: (1) best effort; (2) minimize delay; (3) maximize throughput; (4) maximize reliability; and (5) minimize monetary cost.
Base sites 104 are radio frequency transmitters and receivers that communicate with wireless terminals 102. In addition, base sites 104 are connected to a network of other elements to facilitate the transmission of data, including multimedia data. As shown in
Gatekeeper 112 is preferably a computer that provides control and management functions associated with the wireless channel used for communication between wireless terminals 102 and base sites 104. Dispatch station 118 is preferably a computer that provides access for the dispatcher role associated with the wireless communication systems used for communication between base sites 104 and wireless terminals 102. Web server 114 is preferably a computer that provides a data communications function such as the provision and access to Web pages. Video server 116 is preferably a computer that provides video services to network elements, including wireless terminals 102 and dispatch station 118.
Wireless terminals 102 preferably include a computer 122 coupled to a modem 124. Modem 124 preferably is connected to an antenna 126 to radiate and receive radio frequency signals to implement the wireless communication channel between wireless terminals 102 and base sites 104. Preferably computer 122 implements an Internet protocol which generates packets that are transferred to modem 124. Modem 124 then converts the IP packets into packets or blocks for transmission over the wireless channel using antenna 126 and an associated protocol for the wireless channel.
In accordance with the present invention, the wireless channel provided for communication between wireless terminals 102 and base sites 104 is managed in a manner to provide efficient bandwidth for diverse communications between wireless terminals 102 and base sites 104. In particular, the wireless channel is managed to provide delay-sensitive data with guaranteed bandwidth over the channel and to accommodate non-delay-sensitive data over the same channel. The provision of these functions is discussed below with respect to the preferred embodiments.
In a preferred embodiment, processor 202 preferably is a central processing unit, microprocessor, microcontroller, digital signal processor, or any combination of these. Memory 204 preferably includes volatile and non-volatile memory, including dynamic random access memory, and disk storage. Preferably, network interface 206 implements a TCP/IP network interface for the transmission of Internet protocol (IP) packets
Outgoing channel 402 is divided into slots 406, which occur contiguously over a period of time. Similarly, incoming channel 404 is divided into slots 408, which occur contiguously over a period of time. In the preferred embodiment, outgoing channel 402 has 100 to 400 slots per second occurring where each slot is capable of transmitting about 206 bytes of data. Incoming channel 404 preferably has characteristics that match outgoing channel 402. In a preferred embodiment, a frequency of 746 to 806 megahertz (MHz) is used for wireless channel 400.
To facilitate orderly and efficient use of channel 400 by wireless terminals 102 and base sites 104, slots 406, 408 are preferably organized into slot types, which define a type of data that is transmitted in a particular slot. In contrast to conventional time-division multiplexed channels, slots 406, 408 are not strictly periodically assigned to a particular device or function, rather the assignment of slot types is made selectively and dynamically in a manner to flexibly accommodate varying media and data types. The four slot types defined in a preferred embodiment are random access slots, acknowledgement “ACK” slots, delay-sensitive slots, and non-delay-sensitive slots.
The random access slots are included in incoming channel 404 to allow wireless terminals 102 to reserve or request delay-sensitive slots and non-delay-sensitive slots. Random access slots are also used to transmit data. The random access slots are preferably a slotted-aloha type of slot that is used by wireless terminals 102 as a point of access. In other words, the random access slots are used by wireless terminals to alert a device managing the channel that the wireless terminal has data to be transferred over another slot type. The random access slots are, as the name suggests, randomly accessed by wireless terminals when available, without any arbitration. This allows for the occurrence of collisions between contending wireless terminals.
The delay-sensitive slots carry, as the name suggests, delay-sensitive, streaming data, such as a video data stream or an audio data stream. The non-delay-sensitive slots are allocated for data that is not delay-sensitive, for example Web site pages and the like. Non-delay-sensitive data typically is tolerant of some delay. The non-delay-sensitive slots are used for file transfer and the transmission of other error-intolerant data. The ACK slots are used for the wireless terminals 102 and base sites 104 to acknowledge safe receipt of packets sent over channel 400.
Each wireless terminal 102 and base site 104 has a unique media access control (MAC) address that identifies the device. Since there is competition among the wireless terminals to access the incoming channel slots 408, access must be controlled in some manner. In a preferred embodiment, a channel scheduler is implemented using processor 302, memory 304 and wireless modem 308 to orderly schedule access to incoming slots 408 by wireless terminals 102. More specifically, the channel scheduler determines the allocation of delay-sensitive slots, non-delay-sensitive slots, and ACK slots to particular wireless terminals 102. Most preferably, the outgoing channel 402 includes designations within its slots that specify which incoming channel slots 408 may be used by a particular wireless terminal 102. That is, a wireless terminal 102 determines which incoming slots 408 it may use by decoding this information from a portion of the outgoing channel 402. The random access slots are not dedicated to a particular wireless terminal 102, and therefore may be accessed by any wireless terminal 102. If more than one wireless terminal 102 transmits on a random access slot, a collision occurs, and the access is not subsequently acknowledged. This requires the transmitting wireless terminals 102 to retransmit on another available random access slot, preferably with some random time delay to reduce subsequent collisions.
The outgoing channel 402 has only one transmitter, base station 104. Therefore, there is no contention for transmission on outgoing channel 402. Each wireless terminal 102 that is communicating with channel 400 is required to listen to a portion of outgoing channel 402 and respond to data directed to it, as determined by the MAC address.
A method for allocating or reserving resources on channel 400 for delay-sensitive applications such as audio and video transmission, is described below with respect to
First a delay-sensitive application's requirements are sent to a bandwidth management device (500). This preferably occurs by an application on wireless terminal 102 initiating the transfer of data to other network elements. An exemplary application is an H.323 multimedia call that needs to be placed by a computer 122 of a wireless terminal 102. In accordance with the H.323 standard, certain requirements for the application, such as multimedia call type, codec, codec parameters and traffic profile are generated per the application. If the data transmission is to be directed over the wireless channel, then the modem 124 must initiate an access to the channel. Preferably, the communications between the physical network, modem 124, and the H.323 application occur via a layered network protocol.
Preferably, the access to the channel to transfer the application requirements requires that the wireless terminal 102 gain access to the incoming channel 404. To gain access, wireless terminal 102 must transmit on a random access slot the requirements for the desired application. If the random access slot transmission of the application requirements is successful, that is, there are no collisions, then the request is routed to gatekeeper 112, which preferably serves as the bandwidth management device. Another network element, such as base site 104, alternatively serves as the bandwidth management device.
After gatekeeper 112 receives the application requirements (500), gatekeeper 112 converts the application requirements to channel requirements (502). This requires converting the specified application requirements, such as multimedia call type, codec, codec parameters and traffic profile, into channel resources, that is, slots per second, that will be required for the delay-sensitive application. The actual mapping of application requirements to channel requirements varies. Any suitable alternative is available for converting the application requirements to the channel requirements, including a look-up table indexed on an application requirement or an algorithm to dynamically convert the application requirements to the channel requirements. Preferably, a prior analysis of application requirements or exemplary applications is used to provide a fixed mapping from application requirements to channel requirements, that is, slots per second required.
After the channel bandwidth requirement, in terms of slots per second, is determined (502), the bandwidth management device, gatekeeper 112, determines if the required number of slots per second is available on channel 400. Gatekeeper 112 stores data relating to the amount of bandwidth, or slots per second, available on channel 400. A comparison of the amount of bandwidth being currently used with the amount of bandwidth desired for the new delay-sensitive application determines whether there is bandwidth available on the channel. If the channel requirements cannot be met with the available bandwidth, then the applications request for transmission over the network is denied (506). This terminates the request and call (508), leaving the wireless terminal with the option to retry the request.
On the other hand, if the required channel bandwidth is available (504), then the needed bandwidth, that is, slots per second, is reserved on the channel (510). A method by which bandwidth is actually reserved varies depending upon the actual implementation. A preferred method for allocating the required bandwidth is discussed in detail below with respect to
After the bandwidth is reserved on the channel (510), the application set up can be completed such that the application will proceed with the call (512). Continuing with the H.323 example of an audio/video call, after gatekeeper 112 determines that bandwidth is available (504) and has been reserved (510), a message is sent to the wireless terminal 102 that initiated the request (500). The H.323 application is notified that it should proceed with the call. This message from gatekeeper 112 is sent to wireless terminal 102 via the outgoing channel from base site 104.
After application set up is complete (512), the application proceeds with the call and the system 100 manages the bandwidth accordingly. More specifically, the application on the wireless terminal generates IP packets in accordance with the application and without regard to the channel requirement. These IP packets generated by computer 122 are transferred to modem 124 for formatting and transmission over the incoming channel 404 of wireless channel 400. Typically the IP packets generated by the application must be transmitted in multiple slots over wireless channel 400. Modem 124 repackages the IP packets into slots for the wireless channel. After the data is repackaged for the channel slots, the wireless terminal 102 transmits the channel specific packets in the delay-sensitive slots that are granted to that particular wireless terminal 102.
As the call proceeds and packets are transmitted by the wireless terminal to the communication system 100, the communication system 100 preferably continually assesses the traffic and channel requirements (500). That is, gatekeeper 112, the bandwidth management device, preferably keeps or receives a count of the actual slots per second used by the application. This reflects the actual channel utilization used by the application. This actual channel utilization is preferably compared with the predicted channel bandwidth that is allocated or reserved to determine if an adjustment should be made to the bandwidth allocation. In accordance with this comparison adjustments are preferably made.
In a preferred embodiment as described above, where channel slots are allocated on a device basis, if additional applications require delay-sensitive slots for an application on the device, then a new bandwidth request must be made (518). This new bandwidth request mirrors the request made in step 500, described above. Based on the new bandwidth request, new channel requirements are determined (502) and the call is allowed to proceed if the new bandwidth request can be satisfied (504). If the additional bandwidth is not available, the request for a call is denied (506, 508). If the new bandwidth request can be satisfied, then the bandwidth is reserved (510); the application is set up (512); and the call proceeds (514).
First the channel scheduler determines whether a delay-sensitive slot should be scheduled next to maintain an ideal slot separation based on the allocated or reserved channel bandwidth for delay-sensitive applications (600). The ideal slot separation is calculated by dividing the total number of slots that occur in one second on the incoming channel by the number of slots per second allocated or reserved for delay-sensitive applications for a particular wireless terminal. For example, for an incoming channel running at 100 slots per second, a wireless terminal that has delay-sensitive applications requiring 20 slots per second results in an ideal slot separation of five slots. Delay-sensitive slots should be scheduled to meet the ideal slot separation for a wireless terminal or if the time has passed for a delay-sensitive slot to be allocated to maintain the ideal slot separation, then a delay-sensitive slot is needed (602). A preferred method for calculating ideal slot separation and determining whether a delay-sensitive slot is required is discussed below with respect to
If a delay-sensitive slot is not required (602) then the channel scheduler preferably determines whether an acknowledgment slot is needed (605). The channel scheduler is aware of whether a particular transfer during a slot represents the completion of an application packet, such as an IP packet. For IP packets that require an acknowledgement, the channel scheduler notes when the last slot of the packet data is transmitted and hence knows that an acknowledgement slot should be allocated to acknowledge receipt of the packet. If an acknowledgement slot is required (607), then the next slot is assigned as an acknowledgment slot (608). After the slot assignment is made, the method restarts for a determination of the next slot type (610).
If no acknowledgment slot is needed (607) then the channel scheduler determines whether there are any non-delay-sensitive slots needed (612). The scheduler is aware of the wireless terminals 102 requirements for non-delay-sensitive transfers by virtue of the requests to send non-delay-sensitive transfers, which requests are made over the random access slots. If no outstanding non-delay-sensitive requests are awaiting transfer, then the scheduler knows there are no non-delay-sensitive slots needed, and therefore, assigns the next slot as a random access slot (614). After assigning the random access slot the method restarts to determine the next available slot (616).
If on the other hand, there are non-delay-sensitive slots needed by a wireless terminal, then the scheduler determines whether a maximum random access slot separation has been met (618). The maximum random access slot separation is a predetermined number of non-delay-sensitive slots that may occur before a random access slot is granted. The maximum random access slot separation is used to insure that random access slots, which serve as the point for initiating access by wireless terminals, occur at regular intervals over the incoming channel. If the maximum random access slot separation has not been met (618), then the next slot is assigned a non-delay-sensitive slot (620). After this slot assignment, the method returns to start to determine the next slot (622). On the other hand, if the maximum random access slot separation has been met (618) indicating that the maximum period between random access slots has occurred, then a random access slot is assigned (624). After this slot assignment is made, the method restarts for a determination of the next slot (626).
In a preferred embodiment of the invention, the maximum random access slot separation is stored by the channel scheduler and a counter is initialized to zero after any random access slot is granted. The random access slot counter is incremented by 1 for every non-delay-sensitive slot that is granted after the random access slot is granted. A comparison between the random access slot counter and the maximum random access slot separation value is made to determine whether the maximum random access slot separation has been met. When the maximum random access slot separation is met, then a random access slot is assigned, rather than a non-delay-sensitive slot, as discussed above.
Each counter for a wireless terminal is initialized to zero when the channel bandwidth is allocated or reserved for that terminal (702). The ideal slot separation for each terminal is calculated based on the reserved channel bandwidth (704). The ideal slot separation for a terminal is calculated by dividing the total number of slots that occur in one second on the incoming channel by the number of slots per second reserved or allocated to a particular terminal (see
Each counter for each terminal is incremented by one for each slot that occurs on the incoming channel (706). That is, each counter keeps up with the number of slots occurring on the incoming channel since a slot was granted to the particular wireless terminal. For each slot allocation, the channel scheduler compares each terminal's counter with the terminal's ideal slot separation (708). If none of the terminal's counters is equal to or greater than the terminal's ideal slot separation (710), then no delay-sensitive slot needs to be scheduled by the channel scheduler (712). (See step 602 of
If, on the other hand, any terminal's counter is equal to or greater than the terminal's ideal slot separation (710), then a delay-sensitive slot should be scheduled for the terminal that has its counter value equal to or greater than the ideal slot separation (714). It is possible that more than one wireless terminal will have its counter equal to or greater than the terminal's ideal slot separation at any slot. In this case, the channel scheduler preferably selects one of the terminals to be assigned the delay-sensitive slot. Most preferably, a channel scheduler selects the terminal that has a counter value that exceeds its ideal slot separation by the greatest amount. Ties are resolved by any suitable method that guarantees fair access.
For the wireless terminal that is granted the delay-sensitive slot, its counter is updated or re-initialized with the difference obtained from subtracting the ideal slot separation for that terminal from the counter value at the time the delay-sensitive slot was granted (716). In other words, the counters keep a count of the slots occurring since the last granted slot for a terminal. Once a terminal is granted a slot, the counter must be reset. To accommodate situations where a terminal's counter exceeds the ideal slot separation due to contention from other terminals, the counter is reset with a value that accounts for the wait time for the terminal, which allows the counter to maintain the ideal slot separation. For example, if a wireless terminal's ideal slot separation is 10 and due to contention, the counter for that terminal reaches 12 prior to the terminal being granted a slot, then after a slot is granted to the terminal, the counter is reset with a value of 2 (12-10) such that the new counter value is used to attempt to readjust the time for the next granted slot so that the average time is close to the ideal slot separation. After the delay-sensitive slot is assigned, the next slot assignment is determined (718).
As each slot is allocated on the incoming channel, a comparison is made of the acknowledgment slot delay counters with an acknowledgment slot time out value (806). The acknowledgement slot time out value is a predetermined value entered into the system. The acknowledgement slot time out value reflects an ideal time for acknowledgments to be made. If no acknowledgement slot delay counter has reached the acknowledgement slot time out value (808), then no acknowledgement slot needs to be scheduled on the incoming channel. If on the other hand, an acknowledgment slot delay counter is equal to or greater than the acknowledgement slot time out value (808), then an ACK slot should be scheduled on the incoming channel (812). After an acknowledgment slot is granted for a corresponding acknowledgement slot delay counter, then the counter is stopped or ignored (814).
Chart 1000 shows 8 precedence values, 7 through 0. Row 1008 lists a precedence value of 7, which is the highest priority precedence value. The data type that is preferred for a precedence value of 7 is session based call control data, as listed in row 1008, column 1004. Examples of this data include packets used to set up a voice, audio or video call. Row 1010 lists a precedence value of 6. The data type preferred for this precedence value is network-control data for router protocols, as defined by the existing art. Examples of this data include internal maintenance download data. Row 1012 lists a precedence value of 5. The data type preferred for this precedence value is high priority time critical data, such as emergency voice and video data. Row 1014 lists a precedence value of four. The preferred data type for this precedence value is network-control data for router protocols, as defined by the existing art. Exemplary data used for this precedence value includes non-delay critical packets. Row 1016 lists a precedence value of three, which preferably is used for time-critical (delay-sensitive) data, for example voice and video data. Row 1018 lists a precedence value of 2, which is preferably used for higher priority data, for example, emergency data from an emergency database query. Row 1020 lists a precedence value of 1, which is preferably used for non-emergency data, such as Web browser data and non-emergency database queries. Row 1022 lists a precedence value of zero, which is the lowest priority precedence value and is also a default value inserted into packets not using any particular priority protocol. The zero precedence value allows for backward compatibility with all Internet packets. Any data not otherwise specified for a precedence value of 1 through 7, uses a precedence value of the zero.
In the preferred arrangement, the best effort service type, which is shown in row 1110, uses a default forward error correction on the incoming and outgoing channel (see row 1110, column 1106) and uses a random access slot for incoming channel communications (see row 1110, column 1108). A preferred default forward error correction protocol is a three-quarter rate, convolutional code. Alternative default forward error correction protocols include BCH (Bose-Chaudhuri-Hocquenghem) codes (binary and non binary), Reed-Solomon, Golay, Hamming and other linear block and cyclical codes. By virtue of the error correction selection and the channel access method, the best effort service type provides an acceptable delay vs. reliability trade-off. The best effort service type is a default value, which provides backward compatibility for packets unaware of the service types specified according to the invention.
Preferably, the minimize delay service type, which is shown in row 1112, uses strong forward error correction on both the incoming and outgoing channel. The minimize delay service type uses reserved, delay-sensitive slots for the incoming channel media access method. A preferred protocol for strong forward error correction is a one-half rate, convolutional code. Alternative protocols for strong forward error correction include BCH (Bose-Chaudhuri-Hocquenghem) codes (binary and non binary), Reed-Solomon, Golay, Hamming and other linear block and cyclical codes. The minimize delay service type is preferably used for audio and video data.
Preferably, the maximize throughput service type, which is shown in row 1114, uses no forward error correction on both the incoming and outgoing channel. The maximize throughput service type uses reserved, delay-sensitive slots for the incoming channel media access method. The maximize throughput service type is preferably used for audio and video data, in particular, for audio and video protocols where error correction is handled in a network protocol layer higher than the physical layer protocol. Exemplary audio and/or video protocols are IMBE (Improved Multi-Band Excitation) and H.263 with annexes to include built-in error handling.
Preferably, the maximize reliability service type, which is shown in row 1116, uses the best combination of forward error correction and retransmission techniques for both the incoming and outgoing channels. This provides the highest degree of reliability. The incoming channel media access method is random access.
Preferably, the minimize monetary cost service type, which is shown in row 1117, dynamically selects error correction based on the transmission charges and signal levels. That is, an error correction protocol is selected on the basis of cost and the signal levels associated with the particular transmission. The incoming channel media access method is dynamically selected as reserved (delay-sensitive or non-delay-sensitive) or random access based on monetary charges and signal levels.
If the setup procedure is successful (see
After the type of service field is defined for the packet (1202), the wireless modem selects the packet that will be sent over the wireless channel next (1204). In particular, the wireless modem 124 determines which packet from a plurality of applications will be sent over the wireless channel based on the precedence value for the packet and the service type for the packet. Also, the wireless modem 124 determines which packet will be sent based on the type of slots scheduled by the channel scheduler (see
Base site 104 checks the precedence values and service types of packets it receives for transmission on the outgoing channel. Base site 104 uses the precedence values to determine which packet is sent over the outgoing channel next. For both the wireless modem 124 and base site 104, if there are ties in precedence values, the oldest packet of the highest priority value is sent next over the wireless channel, assuming an appropriate slot type in the channel.
By virtue of the present invention, delay-sensitive applications, such as video and audio transmissions, are allocated bandwidth on a wireless channel to guarantee performance. The applications need not be aware of the wireless channel requirements or protocol. Delay-sensitive applications are allocated resources on the channel to guarantee a channel bandwidth to accommodate an application bandwidth. Packets to be transferred over the wireless channel use a type of service bit field to determine the priority of packets and an error correction and media access method. Advantageously, selective allocation of bandwidth permits efficient management of the wireless channel while guaranteeing performance.
While the invention has been described in conjunction with specific embodiments thereof, additional advantages and modifications will readily occur to those skilled in the art. The invention, in its broader aspects, is therefore not limited to the specific details, representative apparatus, and illustrative examples shown and described. Various alterations, modifications and variations will be apparent to those skilled in the art in light of the foregoing description, but embraces all such alterations, modifications and variations in accordance with the spirit and scope of the appended claims.