US RE42225 E1
A system that provides a wireless broadband connection between base stations and customer sites is described. The system includes indoor units within the base stations and customer sites and communicate across cables to outdoor units. The indoor units link to routers, switches and other devices and services. The outdoor units transmit and receive wireless data and send it to the indoor units. The indoor units control the timing of detector measurements in the outdoor unit by transmitting a regular, repeating control message at a predetermined time. Once the outdoor unit receives the control message, it samples its detectors and reports measurements back to the indoor unit.
1. A wireless communication system having a plurality of base stations and customer sites, wherein data is transferred between saidthe base stations and saidthe customer sites, and wherein saidthe system comprisesuses preset downlink time segments for transmitting saidthe data between the base stations and the customer sites, the system comprising:
an indoor unit comprising a first modem configured to modulate/demodulate data transmitted between the base stations and the customer sites, wherein the indoor unit is adapted to transmit a control message at a predetermined time with respect to saidone of the preset downlink time segments;
an outdoor unit comprising a micro controller and a signal detector, saidthe outdoor unit being adapted to receive the control message and, in response to receiving saidthe control message, read saidthe signal detector during the one of the preset downlink time segments; and
a broadband cable linking the indoor unit to the outdoor unit.
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11. A wireless communication system having a plurality of base stations and customer sites, wherein data is transferred between saidthe base stations and saidthe customer sites, and wherein saidthe system comprisesuses preset downlink time segments for transmitting saidthe data between the base stations and the customer sites, the system comprising:
an indoor unit comprising a first modem configured to modulate/demodulate data transmitted between the base stations and the customer sites, saidthe indoor unit further comprising a programmable memory adapted to transmit a control message at a predetermined time with respect to saidone of preset downlink time segments;
an outdoor unit comprising a micro controller and a signal detector, saidthe outdoor unit being adapted to receive the control message and, in response to receiving saidthe control message, read saidthe signal detector during the one of the preset downlink time segments; and
a broadband cable linking the indoor unit to the outdoor unit.
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18. A method for measuring thea strength of a signal transmitted from a base station to a customer site in a wireless communication system, wherein saidthe wireless communication system hasuses preset downlink time segments for transmitting data from the base station to the customer site, and wherein saidthe customer site comprises an indoor unit and an outdoor unit, saidthe method comprising:
transmitting a message from saidthe indoor unit to saidthe outdoor unit, wherein saidthe message is timed to arrive at saidthe outdoor unit at a predetermined time relative to saidone of the preset downlink time segmentsegments; and
reading a detector in saidthe outdoor unit in response to receipt of saidthe message so that saidthe detector is read during saidthe one of the preset downlink time segmentsegments.
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24. A method for tuning a wireless communication system, wherein saidthe wireless communication system hasuses preset downlink time segments for transmitting data from a base station to a customer site, and wherein saidthe customer site comprises an indoor unit having a processor and an outdoor unit having tunable attenuators, saidthe method comprising:
transmitting a control message from saidthe indoor unit to saidthe outdoor unit, wherein saidthe message is timed to arrive at saidthe outdoor unit at a predetermined time relative to saidone of the preset downlink time segmentsegments;
reading a detector in saidthe outdoor unit in response to receipt of saidthe message so that saidthe detector will be read during said predeterminedthe one of the preset downlink time segmentsegments;
transmitting a response message comprising values from saidthe detector to saidthe indoor unit;
determining the appropriate settings saidfor the attenuators in said outdoor unit;
transmitting a second control message comprising updated attenuator settings to saidthe outdoor unit; and
tuning saidthe outdoor unit based on saidthe updated attenuator settings.
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29. A communication node, comprising:
a first modem configured to modulate and demodulate signals to be transmitted to and from a base station via an outdoor unit; and
a second modem configured to transmit a control message to the outdoor unit at a predetermined time prior to a preset downlink time segment, the control message instructing the outdoor unit to read a signal detector during the preset downlink time segment.
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39. A wireless communication system, comprising:
an indoor unit comprising a modem configured to modulate and demodulate signals transmitted between the wireless system and a remote wireless device, wherein the indoor unit is configured to transmit a control message at a predetermined time with respect to a preset downlink time segment; and
an outdoor unit comprising a signal detector, the outdoor unit being configured to read the signal detector during the present downlink time segment in response to receipt of the control message.
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45. A method to operate a communication node, the method comprising:
modulating and demodulating, by a first modem, signals to be transmitted to and from a base station via an outdoor unit; and
transmitting, by a second modem, a control message to the outdoor unit at a predetermined time prior to a preset downlink time segment, the control message instructing the outdoor unit to read a signal detector during the preset downlink time segment.
46. The method of
transmitting, at the predetermined time, the control message by an indoor unit linked to the outdoor unit.
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1. Field of the Invention
This invention relates to wireless communication systems, and more particularly to a wireless communication system that provides telephone, data and Internet connectivity to a plurality of users.
2. Description of Related Art
Several systems are currently in place for connecting computer users to one another and to the Internet. For example, many companies such as Cisco Systems, provide data routers that route data from personal computers and computer networks to the Internet along conventional twisted pair wires and fiber optic lines. These same systems are also used to connect separate offices together in a wide area data network.
However, these systems suffer significant disadvantages because of the time and expense required to lay high capacity communications cables between each office. This process is time consuming and expensive. What is needed in the art is a high capacity system that provides data links between offices, but does not require expensive communication cables to be installed.
Many types of current wireless communication systems facilitate two-way communication between a plurality of subscriber radio stations or subscriber units (either fixed or portable) and a fixed network infrastructure. Exemplary systems include mobile cellular telephone systems, personal communication systems (PCS), and cordless telephones. The objective of these wireless communication systems is to provide communication channels on demand between the subscriber units and the base station in order to connect the subscriber unit user with the fixed network infrastructure (usually a wired-line system). Several types of systems currently exist for wirelessly transferring data between two sites.
In wireless systems using multiple access schemes, frames of time are the basic transmission unit. Each frame is divided into a plurality of slots of time. Some time slots are used for control purposes and some time slots are used for information transfer. Information is typically transmitted during time slots in the frame where the time slots are assigned to a specific subscriber unit. Subscriber units typically communicate with the base station using a “duplexing” scheme which allows for the exchange of information in both directions of connection.
Transmissions from the base station to the subscriber unit are commonly referred to as “downlink” transmissions. Transmissions from the subscriber unit to the base station are commonly referred to as “uplink” transmissions. Depending upon the design criteria of a given system, the prior art wireless communication systems have typically used either time division duplexing (TDD) or frequency division duplexing (FDD) methods to facilitate the exchange of information between the base station and the subscriber units. Both the TDD and FDD duplexing schemes are well known in the art.
In TDD systems, duplexing of transmissions between a base station and its subscriber units is performed in the time domain. A selected subscriber unit typically communicates with a selected base station using a specific pre-defined radio frequency. The channel is time-divided into repetitive time periods or time “slots” which are employed for uplink and downlink transmissions. In contrast to FDD systems, frequency allocation or frequency reuse patterns are simplified because there is no requirement of frequency separation between the uplink and downlink transmissions.
Both the uplink and downlink transmissions occur during different pre-determined time slots using the identical radio frequency. In some current wireless communication systems, there are base stations that act as central points for receiving and transmitting data to a plurality of customer sites. These base stations typically connect to other data systems such as the Internet, the phone system or other systems that provide user data to the customer's sites. As can be imagined, it is important to maintain a strong signal between the base station and the customer sites. Thus, in conventional systems, power detectors within the base station and customer sites continually monitor wireless transmissions in order to tune the system to receive the strongest possible signal.
Unfortunately, prior customer sites relied on complicated control signals to measure transmission power levels. These control signals were implemented because in TDD systems the transmit and receive paths use the same frequency. Thus, it was possible that when the customer site equipment took a power measurement, it was actually measuring a transmission signal from a nearby customer site that was transmitting on the same frequency. The addition of the control signals ensured that power measurements were taken from the base station, and not a nearby customer site.
Moreover, in some prior systems, the customer site equipment was separated into indoor units and outdoor units. The indoor units typically included the modem and electronics for connected with the customer's equipment. The outdoor unit was installed on the exterior of the building and included the antenna for receiving and transmitting wireless user data. However, in these systems, the outdoor unit did not independently know when the base station was transmitting.
Some prior systems attempted to solve this problem by including a gating signal between the indoor unit and the outdoor unit. The gating signal could be used to instruct the outdoor unit to sample its receive detectors at a particular time, thus ensuring that the receive detectors would measure signals from the base station. Unfortunately, adding this signal to the transmission cable between the outdoor unit and the indoor unit requires costly hardware changes. In addition, transmitting the extra gating signal across the transmission cable increases spurs and other undesirable effects in the data transmission pathway.
This problem is compounded by the fact that the outdoor unit does not contain a modem. A modem could serve as a conduit for the outdoor unit to receive additional commands. Thus, the outdoor unit, by itself, cannot determine the proper time to sample the receive detectors.
Thus, what is needed in the art is a convenient system at the customer site for accurately measuring the power of transmission signals from the base station. Such a system is described below.
One embodiment of the invention is a wireless communication system having a plurality of base stations and customer sites, wherein data is transferred between said base stations and said customer sites, and wherein said system comprises preset downlink time segments for transmitting said data between the base stations and the customer sites. This embodiment includes: an indoor unit comprising a first modem configured to modulate/demodulate data transmitted between the base stations and the customer sites, wherein the indoor unit is adapted to transmit a control message at a predetermined time with respect to said preset downlink time segments; an outdoor unit comprising a micro controller and a signal detector, said outdoor unit being adapted to receive the control message and, in response to receiving said control message, read said signal detector; and a broadband cable linking the indoor unit to the outdoor unit.
Another embodiment of the invention is a wireless communication system having a plurality of base stations and customer sites, wherein data is transferred between said base stations and said customer sites, and wherein said system comprises preset downlink time segments for transmitting said data between the base stations and the customer sites. This embodiment includes: an indoor unit comprising a first modem configured to modulate/demodulate data transmitted between the base stations and the customer sites, said indoor unit further comprising a programmable memory adapted to transmit a control message at a predetermined time with respect to said preset downlink time segments; an outdoor unit comprising a micro controller and a signal detector, said outdoor unit being adapted to receive the control message and, in response to receiving said control message, read said signal detector; and a broadband cable linking the indoor unit to the outdoor unit.
Yet another embodiment of the invention is a method for measuring the strength of a signal transmitted from a base station to a customer site in a wireless communication system, wherein said wireless communication system has preset downlink time segments for transmitting data from the base station to the customer site, and wherein said customer site comprises an indoor unit and an outdoor unit. This method provides: transmitting a message from said indoor unit to said outdoor unit, wherein said message is timed to arrive at said outdoor unit at a predetermined time relative to said preset downlink time segment; and reading a detector in said outdoor unit in response to receipt of said message so that said detector is read during said preset downlink time segment.
Still another embodiment of the invention is a method for tuning a wireless communication system, wherein said wireless communication system has preset downlink time segments for transmitting data from a base station to a customer site, and wherein said customer site comprises an indoor unit having a processor and an outdoor unit having tunable attenuators. This method includes: transmitting a control message from said indoor unit to said outdoor unit, wherein said message is timed to arrive at said outdoor unit at a predetermined time relative to said preset downlink time segment; reading a detector in said outdoor unit in response to receipt of said message so that said detector will be read during said predetermined downlink time segment; transmitting a response message comprising values from said detector to said indoor unit; determining the appropriate settings said attenuators in said outdoor unit; transmitting a second control message comprising updated attenuator settings to said outdoor unit; and tuning said outdoor unit based on said updated attenuator settings.
Like reference numbers and designations in the various drawings indicate like elements.
Throughout this description, the preferred embodiment and examples shown should be considered as exemplars, rather than as limitations on the present invention.
As described above, embodiments of the present invention relate to a broadband wireless communication system. The system is particularly useful for linking a plurality of customers and businesses together to share data or access the Internet. In general, the system provides base stations that are centrally located from a plurality of customer sites. The base stations are linked to services desired by customers, such as Internet access, satellite access, telephone access and the like. Within the base stations are communication devices, such as routers, switches and systems for communications with the desired services. In addition, each base station includes one or more antennas for connecting wirelessly with one or more customer sites.
A customer desiring, for example, access to the Internet will install a set of Customer Premises Equipment (CPE) that includes an antenna and other hardware, as described in detail below, for providing a high speed wireless connection to one or more base stations. Through the high-speed wireless connection, the customer is provided with access to the Internet or to other desired services. As discussed below, the data transmitted wirelessly between a base station and a customer site is termed herein “user data”. Of course, at each customer site, a plurality of simultaneous computers can be provided with wireless access to the base station through the use of hubs, bridges and routers.
In one embodiment, the base station comprises a plurality of indoor units that provide an interface between the routers, switches and other base station equipment and a plurality of outdoor units (ODU) that transmit/receive data to/from the customer sites. Each indoor unit typically includes, or communicates with, a modem for modulating/demodulating user data going to/from the outdoor unit.
In one embodiment, each of the indoor units is connected to only one outdoor unit and each IDU/ODU pair transmits and receives user data with a unique frequency. This format provides a base station with, for example, 10, 20, 30 or more IDU/ODU pairs that each communicate with customer sites using unique frequencies. This provides the base station with a means for communicating with many customer sites, yet dividing the bandwidth load between several frequencies. Of course, a base station that serves a small community of customer sites might only have a single IDU/ODU pair.
Each ODU at the base station is normally located outside of the physical building and includes an integrated broadband antenna for transmitting/receiving wireless user data packets to/from the customer sites. Of course, the antenna does not need to be integrated with the ODU, and in one embodiment is located external to the ODU.
The ODU and the IDU communicate with one another through a broadband cable connection, such as provided by an RG-6 cable. In one embodiment the ODU and IDU communicate across about 10 to 100 feet of cable. In another embodiment, the ODU and IDU communicate across about 100 to 500 feet of cable. In yet another embodiment, the ODU and the IDU communicate across about 500 to 1000 feet of cable.
In one embodiment, the IDU controls functions within the ODU by sending control messages in addition to the user data stream. The IDU passes messages to the ODU in order for the IDU to control certain aspects of the ODU's performance. For example, the IDU may determine that the system needs to be tuned in order to maximize the signal strength of the user data being received. The IDU will send a control message in the form of a frequency shift key (FSK) modulated signal, as described below, to the ODU along the broadband cable. The control message preferably includes the identity of a variable voltage attenuator (VVA) or other type of attenuator in the ODU and a new setting for the designated VVA. An onboard micro controller in the ODU reads and interprets the control message coming from the IDU and sends the proper signals to the designated VVA.
Once the ODU has adjusted the designated VVA, the micro controller in the ODU sends a response in the form of a response message back along the broadband cable to the IDU. The response message preferably includes a confirmation of the new VVA setting, or other data to confirm that the requested control message has been fulfilled. The following discussion provides a detailed listing and the structure of exemplary control messages and response messages that can be transmitted between the IDU and the ODU.
The ODU in a CPE preferably samples its transmit detectors only during a transmission to the base station i.e. during an uplink. Fortunately, the ODU knows when it is transmitting user data, so it can accurately sample transmit detectors during an ODU transmission.
In addition to sampling its transmit detectors, the ODU needs to sample its receive detectors to tune the ODU to optimally receive the signal from the base station.
Of course, the ODU should only sample the receive detectors during a transmission from the base station i.e. during a downlink. Unfortunately, in a TDD system there are transmissions at the same frequency from other customer premises ODUs directed to the base station. Because both the uplink transmissions and the downlink transmissions are on the same frequency in a TDD system, the customer premises ODU cannot continuously monitor downlink signals because the ODU might receive a transmission from a nearby CPE that is at a higher signal strength than the ODU receives from the base station. If this happened, the ODU might improperly intercept the transmission from a nearby CPE and proceed to sample its receive detectors at a time other than during transmission from the base station.
As described in detail below, embodiments of the invention include communication systems that only sample receive detectors in the ODU during times that are known to be during a downlink from the base station to the CPE. These embodiments send regular control messages from the IDU to the ODU that request detector values that are measured at a guaranteed downlink transmission time within the TDD frame. By only sampling the receive detectors during this guaranteed downlink transmission time, the ODU in the customer premises equipment is ensured of reading the base station transmission and not a transmission from a nearby CPE outdoor unit. It should be realized that the base stations and the customer sites each have indoor units and outdoor units that function similarly to provide a communication link between the external antenna and the electronic systems in the interior of the buildings. Of course, in one embodiment within the customer sites, the indoor units are connected through routers, bridges, Asynchronous Transfer Mode (ATM) switches and the like to the customer's computer systems, which can also include telecommunication systems. In contrast, within the base stations the indoor units are connected to the routers, switches and systems that provide access to the services desired by the customers.
Referring now to
Each cell 102 within the wireless communication system 100 provides wireless connectivity between the cell's base station 106 and a plurality of customer premises equipment (CPE) located at fixed customer sites 112 throughout the coverage area of the cell 102. The customer premises equipment normally includes at least one indoor unit (not shown) and one customer ODU 110. Users of the system 100 can be both residential and business customers. Each cell can service approximately 1,000 residential subscribers and approximately 300 business subscribers. As will be discussed below, each customer ODU 110 is positioned to receive and transmit user data from and to one of the base station ODUs 107. As discussed above, the customer IDU (not shown) is located within the site 112 and provides a link between the customer's computer systems to the ODU.
As shown in
The wireless communication of user data between the base station ODUs 107 and customer ODU 110 within a cell 102 is advantageously bidirectional in nature. Information flows in both directions between the base station ODUs 107 and the plurality of Customer ODU 110. Each of the base station ODUs 107 preferably broadcast single simultaneous high bit-rate channels. Each channel comprises different multiplexed information streams. The information in a stream includes address information which enables a selected Customer ODU 110 to distinguish and extract the information intended for it.
The wireless communication system 100 of
The wireless communication system 100 of
1. Cell Site
The base station can also alternatively include a video server 128 and direct broadcast satellite (DBS) receiver equipment 130. The back-haul interface equipment 124 allows the base station to bi-directionally communicate with the hub 114 (FIG. 1).
The base station 106 is preferably modular in design. The modular design of the base station 106 allows the installation of lower capacity systems that can be upgraded in the field as capacity needs dictate. The IDU 122 in conjunction with the ODU 108 performs both the media access protocol layer and the modulation/de-modulation functions that facilitate high-speed communication over the wireless link. The IDU 122 preferably is connected via the broadband cable 129 to the base station outdoor unit 108 which is preferably mounted on a tower or a pole proximate the base station 106. The base station outdoor unit 108 contains high-frequency radio electronics (not shown) and antenna elements for transmitting user data to the customer sites.
2. Indoor Unit
The modem 135 includes a Field Programmable Gate Array (FPGA) 136 that stores instructions for controlling other subcomponents of the IDU 122. For example, the FPGA 136 communicates with a Frequency Shift Key (FSK) modem 138 in order to send FSK modulated control messages from the EDU through the broadband cable 129, to the outdoor unit 108. A low band pass filter 139 is provided between the cable 129 and the FSK modem 138. In an alternate embodiment, an Application Specific Integrated Circuit (ASIC) replaces the FPGA in order to provide similar functions.
As is discussed in detail below, the IDU and ODU communicate with one another using messages. The IDU sends control messages to the ODU, and the ODU responds with response messages. This communication allows the IDU to request data from ODU detectors, and then send commands instructing the ODU to reset subcomponents in order to be more efficient.
Thus, control messages are FSK modulated and sent from the IDU to the ODU. Similarly, response messages from the ODU to the IDU are demodulated by the FSK modem 138 and then interpreted by instructions with the FPGA 136. These control messages and response messages, and their data structure and format, are discussed in detail below. In one embodiment, the transmission baud rate of the FSK modem 138 is 115 kbps with one start bit, one stop bit and one parity bit. Of course, other data transfer speeds and formats are contemplated to be within the scope of the invention. Moreover, the FSK modem 138 preferably transmits and receives in frequencies between 6-8 MHz.
Messages between the IDU and ODU are preferably transmitted independently of the other signals being passed along the cable 129. In one embodiment, the ODU acts like a slave in that it does not originate messages, but only responds to control messages it receives from the IDU.
As illustrated, power is provided to the ODU through a DC power supply 140 that provides, in one embodiment, 48V DC to the ODU. A 20 MHz reference signal 142 is also transmitted across the cable 129 in order to keep components in the IDU and ODU synchronized with one another.
The communications processor 132 is also linked to an Input/Output port 150 that attaches to the routers, switches and systems within the base station. The communications processor 132 receives packet data from the Input/Output port 150 and transmits it to a modem 153 for modulation demodulation. The modulated data signal is then placed on a 140 MHz main signal 154 for high throughput transmission to the ODU 108. It should be realized that the data transmission along the 140 MHz main signal can occur simultaneously with the control message and response message data that is Frequency Shift Key modulated across the cable 129.
In order for the IDU and ODU to effectively and rapidly switch between receiving and transmitting data modes, a 40 MHz switching signal 158 is also linked to the communications processor 132 and carried on the cable 129. The 40 MHz switching signal 158 is used within the system to switch the ODU and IDU from transmit to receive mode, as will be discussed below with reference to FIG. 4.
In one embodiment, if the 40 MHz signal is present, the ODU and IDU enter transmit mode to send user data from the base station ODU to customer ODUs. However, if the 40 MHz signal is not present, the ODU and IDU enter receive mode wherein user data being transmitted from other ODU's is received by the base station ODU. The timing of the switching signal is controlled by instructions residing in the FPGA 136. For example, in a half-duplex Time Division Duplex architecture, the switching signal 158 is preferably set to switch between receive and transmit modes. However, in a full duplex architecture where user data is constantly being received, the switching signal 158 can be programmed to switch between a transmit mode and a null mode.
3. Outdoor Unit
Still referring to
The microcontroller 400 communicates with a multiplexer 170 that separates the signals carried on the cable 129. Within the microcontroller 400 is a programmable memory 161 that stores instructions for gathering the response data and forming response messages for transmission to the IDU. In addition, the instructions within the memory 161 read incoming control messages from the IDU and send control signals to sub-components of the ODU. A FSK modem 165 is connected to the multiplexer 170 and microcontroller 400 for modulating/demodulating messages to/from the IDU. As shown a Universal Asynchronous Receiver/Transmitter (UART) 166 is connected to the modem 165 and receives modulated serial data from the multiplexer 170.
a. Transmit Mode
If the ODU is in transmit mode, the modulated user data being sent from the IDU along the 140 MHz main signal is first routed through the multiplexer 170 to the switch 160a. If the switch is set to transmit mode, the main signal is sent to an IF UP CONVERSION block 200 that converts the 140 MHz signal to an approximately 2.56 GHz (S band) signal. As illustrated, the IF UP CONVERSION block 200 first provides a variable voltage attenuator (VVA) 210 that is used to compensate for frequency fluctuations from transmission along the cable 129. The signal then passes to a detector 212 that measures power levels after compensation at the cable input.
Although the following discussion relates to a system that transmits user data within the millimeter band at frequencies of approximately 28 GHz, the system is not so limited. Embodiments of the system are designed to transmit user data at frequencies, for example, of 10 GHz to 66 GHz.
The user data signal is then up-converted to an S band signal at an IF UP CONVERSION block 216 through an associated local oscillator block 219. The local oscillator block 219 preferably includes an S band frequency generator 220. In one embodiment, the frequency generator 220 includes a National Semiconductor LMX 2301 or Analog Devices ADF41117. The signal is then sent through a second VVA 234 that is used for power adjustment at the S band frequency.
Once the signal has-been up-converted to the S band frequency, it is sent to an RF UP CONVERSION block 250. The RF UP CONVERSION block 250 links to a millimeter wave band frequency generator 255 within the local oscillator block 219 for up-converting the 2.56 GHz signal to an approximately 28 GHz signal. The up-converted signal is then passed through a VVA 264 to provide for millimeter wave band power adjustment. Once the signal has been adjusted by the VVA 264 it is sent to a Power Amplifier 268 and then to an output power detector 269. The signal is then finally passed through the switch 160b and out an antenna 270.
b. Receive Mode
If the ODU is in receive mode, user data is received along a 28 GHz signal (LMDS band) and passed through the antenna 270 and into an RF DOWN CONVERSION BLOCK 272. Within the RF DOWN CONVERSION BLOCK 272 is a Low Noise Amplifier (LNA) 275 which boosts the received 28 GHz signal. The signal is then sent to a VVA 280 for power adjustment at the millimeter wave band after the LNA 275. The received 28 GHz signal is then sent to a RF down converter 285 for down conversion to a 2.56 GHz (S band) signal. The RF down converter 285 communicates with the Local Oscillator block 219 to reduce the incoming signal to the S band range.
After the received signal has been down converted to 2.56 GHz, it is transmitted to an IF DOWN CONVERSION block 290. Within the IF DOWN CONVERSION BLOCK 290 is a VVA 292 for adjusting the power at the S band prior to down conversion. Following adjustment by the VVA 292, the received signal is passed to a detector 294 for measuring power leakage from the transmission path during signal transmission. The signal is then passed to an IF down converter 298 which uses the local oscillator block 219 to down convert the S band signal to a 140 MHz signal for transmission across the cable 129.
After being converted to a 140 MHz signal, the received user data is passed through another VVA 300 for power adjustment at the low frequency band and then a detector 304 to measuring power levels before transmission across the cable 129 (4 dBm at the cable output).
c. Message Traffic Between the ODU and IDU
It should be realized that the control messages sent by the IDU to the ODU can control components of the ODU. For example, in one embodiment, the controlled components in the ODU are the VVAs and frequency synthesizers. Response messages from the ODU to the IDU are also generated to include data from the detectors, temperature sensor and other components described above. As can be imagined, control messages are sent by the IDU and then interpreted by the microcontroller in the ODU. After interpreting the message, the microcontroller sends the appropriate adjustment signals to components of the ODU.
As shown in
The micro controller 400 is also in communication with the local oscillator block 219. In addition a digital to analog (D/A) converter 415 communicates with the micro controller 400 in order to control the VVAs within the ODU. In one embodiment, the D/A converter is an Analog Devices model AD8803 D/A converter.
The micro controller 400 also provides an input from a temperature sensor in order to provide for temperature compensation of the ODU measurements. In one embodiment, the temperature sensor is a National Semiconductor LM50 temperature sensor.
As discussed previously, the IDU transmits FSK modulated control messages to the ODU to control particular components. The structure and format of the control messages sent by the IDU and the response messages returned by the ODU are discussed in detail below.
In one embodiment, the maximum data rate of FSK modulated messages that can be handled by the Micro Controller is 125 Kbps. However, in another embodiment, and for compatibility with a conventional personal computer, FSK data is transmitted at a 115.2 kbps data rate. Accordingly, the protocol between the Micro Controller 400 and communications processor 124 can be kept as simple as possible and at the same time flexible for future changes. The message structure presented in the following section takes into account this flexible simplicity. In general, the messages passed between the ODU and the IDU are delivered byte after byte with no delay. In one embodiment, in the ODU, a time gap of more then 0.5 msec between bytes will cause the ODU to re-synchronize on the next preamble.
1. Message Structure
In one data format, each message, starts with a fixed preamble that is used to identify the beginning of a message. Following the preamble an identifier is sent. The identifier is unique per message, i.e., a specific identifier defines completely the structure of the following message information fields.
The variable information within each message is preferably sent after the identifier. In addition, a CRC is added at the end of each message as an integrity check of the message. The Micro Controller 400 in the ODU receives a control message from the IDU, controls the required components in the ODU and prepares a response message. As soon as the IDU finishes sending the control message to the ODU, it switches from transmit mode to receive mode. The ODU then begins to transmit FSK modulated response messages to the IDU.
One embodiment of a data structure of the messages is as follows:
In general, the messages are delivered byte after byte with no delay. When the ODU detects an error, it waits until the next preamble. No response messages are sent back from the ODU to the IDU.
2. Message Traffic
In order to keep the protocol simple, only one control message and one response message are preferably used during normal operation mode. This “MEGA” control message/response message includes all the possible basic control/response messages. Additional control messages are needed for such functions such as software updates and technical information such as IDU, ODU serial numbers and software versions. If new control or response messages are needed in the future, they can be easily implemented by following the data structure represented above. Table 1 lists preferable control/response messages and their unique identifiers.
In the following tables that describe message data fields, it is assumed that the messages start with a preamble and identifier, and end with an 8 bit CRC that is aligned to be in it's own byte.
a. Master Control Message
The Master control message is used in the initialization state for an IDU to identify itself as a Master IDU. During a master IDU configuration, the CPE preferably monitors the IDU/ODU link for a few milliseconds to determine if there is already a master present. The ODU then responds with the same message.
b. Identify Control Message
The Identify control messages has no fields, but is simply the preamble, identifier (0×12), and CRC sent from the IDU to the ODU.
c. Identity ResDonse Message
The Identity response message is the ODU's response to the Identify control message from the IDU.
d. Unexpected Response Message
The Unexpected Response Message is the response to a valid control message which is not expected in the current mode. For example, receipt by the ODU of a Mega Control message during initialization, as could happen after a spontaneous reset of the ODU.
e. Set Mode Control Message
The Set Mode control message is used by the IDU to change the state of the ODU. The ODU responds by repeating the Set Mode message to the IDU as a response message.
f. Test Control Message
The Test Control Message is used by the IDU to instruct the ODU to perform some kind of test operation as described below. The general form of the message is shown in the table below:
To conduct testing of the ODU it is useful to have the ODU generate either of the continuous tones corresponding to a 0 or a 1. The format is shown in the table below:
The FSK tone generation operation causes the ODU to generate either a continuous ‘0’ tone, or ‘1’ tone for the specified number of seconds.
While the tone is being generated the ODU will not respond to control messages since the link is half duplex. When the specified time has elapsed the ODU will resume listening for control messages from the IDU.
ii. Test Control Message—Request Break Status (FSK Cut-off Frequency)
This command determines from the ODU if a “break” character has been detected on the ODU/IDU message interface. The table below shows the format of this message.
In virtually all cases, the ODU responds with a Test_Command:Break_Status_Report, indicating if it has detected a “break” character since the last request or not. The message is used to test the ODU FSK receive modem function. A “break” character being detected is the result of the ODU detecting a continuous series of zeros. This can only happen by an external source injecting a pure low tone into the ODU.
The cut-off frequency of ODU receive circuitry can be determined on a test stand by injecting different frequency tones onto the response data interface and repeatedly requesting the ODU detected a “break” character. Eventually a frequency will be reached where the ODU does not detect a break—hence the cut-off can be determined.
iii. Test Control Message—Break Status Report
This message is the response to the Request Break Status and is shown in the table below:
This message contains the response to the Test Control—Tune Test. It's layout is show below:
The Tune test message attempts to tune the ODU to the specified frequency without regard to the valid frequency range for the ODU, therefore tuning outside of the normal range is permitted. The step resolution of the command is 100 kHz. No range checking is performed so specifying values too far beyond the valid range may have unpredictable results. The ODU may not be able to tune to the precise frequency specified, when this occurs it tunes to the nearest frequency it can.
g. Tune Control Message
The Tune Control instructs the ODU to tune to a given frequency specified in units of 100 kHz. The ODU responds after performing the tuning operation by echoing the same Tune Control message back to the IDU and reporting the frequency to which the ODU is now tuned. If the specified frequency is outside the valid frequency range for the ODU, the ODU does not retune. Therefore specifying a frequency of 0 is a mechanism for querying the ODU as to the frequency to which it is tuned without changing the frequency.
The frequencies of 1 and 4294967295 (or FFFFFFFF hex) are reserved as special query-mode frequencies. If the ODU is told to tune to 0.0001 GHz, the ODU will not retune but will respond with the minimum available frequency. For instance, a 28 GHz ODU would return the number 272000. If the ODU is told to tune to 429496.7295 GHz, it will not retune but will respond with the maximum available frequency, or 286500 for a 28 GHz ODU.
The ODU may not be able to tune to the precise in-band frequency specified, when this occurs it truncates the value to the nearest possible frequency and tunes to that frequency instead.
h. Mega Control Message
The Mega Control is used by the IDU to instruct the ODU to change the values of Attenuators or the Frequency.
i. Mega Response Message
The Mega Response message is the response to the Mega Control message.
j. Mega VVA Control Message
The Mega VVA Control is used by the IDU to instruct the ODU to change the values of Attenuators and the Frequency. Unlike the Mega Control message, it contains the explicit VVA settings.
k. Mega Det Message
The Mega Det message is the response to the Mega VVA control.
l. Download Control Message
The Download Control message is used by the IDU to instruct the ODU to perform some kind of test operation. The general form of the message is shown in the table below:
The ODU maintains a buffer in its internal RAM for accumulating data to be written to flash memory. This is called the ROW buffer, and is preferably 64 bytes in size. It is sub-divided into 8 blocks, each of which is 8 bytes. A block is updated using this Update Block operation. The format of the operation is defined in the table below:
This message initiates an attempt to write the current content of the ROW buffer in the ODU to flash memory. The format of the operation is defined in the table below:
This message reads up to 4 bytes from the specified address in memory. The format of the operation is defined in the table below:
This message instructs the ODU software to reset. Control is immediately passed through to the address specified in the reset vector. This mimics behavior at power up. There can be a response to this message. If successful, the ODU will behave as is it has just powered on, if not, it will still be in the same state it was before the reset command had been issued. The format of Software13 Reset is defined in the table below:
This message requests partition information on the specified partition number. The ODU responds with a download13 ack:partition_info_report message containing the partition information requested. The format of get13 partition_info is defined in the table below:
This message requests the ODU to calculate a 16 bit CRC be calculated over the specified range. The IDU uses the request to verify a partition after it has been downloaded. The ODU responds with a download13 ack:CRC13 Report message containing the calculated CRC. The format of packet is defined in the table below:
This message requests the address of the ODU ROW buffer. It is used by external software manipulating configuration and hardware parameters to retrieve the values of individual parameters from the ROW buffer using the Download:Peek13 Memory command as its most primitive operation. The ODU responds with a Download_Ack: Row_Buffer Address packet. The format of Get_Row_Buffer_Address is defined in the table below:
m. Download Ack Control Message
This message contains the response from the ODU to download commands that generate a response.
i. Download Ack Control Message—Memory Report
This message is the response to a download:peek_memory command. It returns up to 4 bytes from the specified address in memory. The format of the operation is defined in the table below:
This message is the response to a download_get_partition13 info command. It returns partition information for the partition number requested. The format of partition13 info13 report is defined in the table below:
This message describes the ODU result of a Download: Write13 Row processed by the ODU. Normally a write will succeed and the status below will return 0. If one or more blocks were not updated, or the ODU was unable to write all the blocks to flash memory correctly, it will respond with a status of 1, and the “Bit13 Vector” field will indicate which blocks the ODU has. A ‘1’ in a bit position indicates the block is present, a ‘0’ indicates its absence. The remedy to this condition is to resend the missing blocks, and the attempt the write again. The format is shown below:
This message reports a 16 bit CRC calculated by the ODU in response to a previous Download:Request13 CRC command. The format of packet is defined in the table below. The ODU includes the starting address and the length to identify the CRC being reported.
This message is in response to a previous Download:Update13 Block. The format of the packet is defined in the table below. There are no conditions when an update should not be successful. The only possibility for not receiving a Download13 Ack:Block_Updated message is that the ODU did not receive the Download:Update_Block request. The remedy is to re-send the packet.
This message is the response to the Download:Get_Row_Buffer_Address command. It provides the absolute address of the Row buffer, which is where Calibration and Hardware parameters are maintained at runtime. This enables suitable external software to make temporary changes to the operating values of these parameters and observer their effect on the system, without writing them to flash memory (an operation most often performed when an ODU is being calibrated). The format of the packet is defined in the table below:
When the ODU detects an error in the control message, it normally discards the message. Since all control messages that are sent by the IDU are responded to by the ODU, the IDU detects the failure to receive a response message via a timeout.
The IDU, when acting as initiator, sends control messages and then waits for message responses. If the IDU doesn't receive any response messages after, for example, two (2) milliseconds, it resends the control message again. If it doesn't receive any response messages after sending several control messages in a row, the IDU takes appropriate corrective action.
4. Control of ODU Components
Table 30 summarizes the components that may be controlled in the ODU by the IDU, their characteristics and the number of bits required to set/read their values.
Table 31 summarizes the response messages that can be sent from the ODU to the IDU. The bits used to control/read items are not necessarily what will appear in the user data making up the protocol.
Referring now to
On a power-on, or when a watchdog timer expires, the ODU resets and enters a preliminary checkout phase. This phase is explained more completely with reference to FIG. 7. Briefly, all peripherals are reset to a benign state and the ODU places itself in Mode 6 (504). The ODU then automatically attempts to transition itself to Mode 7 (506). This transition entails performing a CRC test on all memory partitions in the ODU to verify that the flash memory is correct and consistent. If it is correct, the initialization procedure in each partition is invoked. This verifies that the content of the memory partition is compatible with the content of any other memory partitions on which it depends. If all memory partitions report compatibility the boot code transition is successful and the system moves to Mode 7, otherwise it remains in Mode 6.
If the process 501 moves to Mode 7, a set13 mode command is given by the micro controller and the system initiates normal operation by transitioning the ODU to Mode 0 (512). From Initialization Mode 6, the only valid transition to Mode 0 is through Mode 7, which requires all the previous system tests be successful.
Note that in the State Diagram in
While in Mode 0, the process 501 can also transition to a loopback Mode 2 (516) and to a normal operational Mode 1 (520). These other Modes are discussed more completely in reference to
2. Preliminary Checkout (Mode 6)
Once this is complete, the IDU 122 sends a SET13 MODE (7) control message that attempts to transition the ODU from the checkout mode 6 into Mode 7. The ODU responds with a response message indicating its current mode. A determination of the ODU's current mode is then made by the IDU 122 at a decision state 610. If a determination is made that the ODU is still in Mode 6, and did not transition to Mode 7, the checkout process 600 moves to a state 614 to begin downloading new software to the ODU in an attempt to help the ODU transition to Mode 7.
However, if a determination was made at the decision state 610 that the ODU was not still in Mode 6, the IDU then issues a SET13 MODE (0) control message to move the ODU into its operational mode (0). The checkout process 600 then terminates at an end state 616.
When the IDU issues the SET13 MODE (0) command, it learns several pieces of information from the response message. If there's no response it indicates thateither the connection to the ODU is faulty or that the ODU is broken in some way. If there is a response, then the state returned in the response message indicates which of the three possible states the ODU is now in. From the response message the IDU can determine if it must perform some remedial action on the ODU (see the download procedure described later), or if it can begin operation.
3. Handshaking Process
After the initialization processes of
The IDU then issues a SET13 MODE (1) control message to transition the ODU into Normal Operational Mode 1. This transition results in the ODU performing the following functions:
Measure test points.
Once complete, the process 800 then loops continuously, receiving response messages from the ODU and performing the actions dictated by the control messages from the IDU. The most typical action in this process in the ODU is:
As shown in
A determination is then made at a decision state 934 whether or not the LinkAcquired bit was set in the Mega Control message. If the LinkAcquired bit was set, the ODU reports the measurement taken immediately after the detector reset at a state 938. However, if the LinkAcquired bit was zero, the ODU reports the measurement taken immediately before the detector reset at a state 940.
The process 900 then waits two milliseconds at a state 942 and proceeds to sample any remaining detectors in the ODU at a state 944. The Mega response message is then sent from the ODU to the IDU.
5. Loopback Mode
In the loopback mode process 1000 illustrated in
6. Customer Premises Equipment
Although the previous discussion has focused on IDUs and ODUs that are installed as part of a base station, these devices are similarly installed within each customer site for receiving and transmitting wireless data. As illustrated
As shown in
The NIU 1146 performs the necessary communication interface functions including airlink and protocol interface functions to allow the residential user access to the network. The service gateway unit 1148 allows the residential user to gain access to the services provided over the communications system.
For example, as shown in
Similarly, by interfacing with copper or co-axial wiring 1149 within the residence 1144, the residential gateway 1142 is capable of providing 10-baseT and other data services to equipment 1150 (such as a personal computer depicted in
The communication interfaces of the business gateway 142′ are similar to those of the residential gateway 1142 (FIG. 12). However, the service interfaces of the business gateway 142′ differ from those of the residential gateway 1142. The business gateway 142′ includes interfaces capable of driving voice and data services typically used by small business customers. These include integrated services digital network (ISDN), local area network (LAN), PBX switching and other standard voice and data services.
As shown in
Alternatively, the wireless functionality provided by the business gateway 142′ can be integrated into the multi-service concentrator 1156 in order to reduce costs and provide a more integrated business gateway solution. Different types of multi-service concentrators 1156 can be used depending upon the size and needs of the business customer. Thus, a network provider can deploy a cost effective solution with sufficient capabilities to meet the business customer's needs.
Various types of services can be provided to the business customer using the CPE 110′ of FIG. 11. For example, by providing standard telephone company interfaces to the business customer, the business CPE 110′ gives the customer access to telephone services yet only consumes airlink resources when the telephone services are active. Network providers therefore achieve significant improvements in airlink usage efficiency yet are not required to modify or overhaul conventional interfaces with the business customer's equipment (e.g., no changes need to be made to PBX equipment). In addition, the business gateway 142′ can support HSSI router and 10-BaseT data interfaces to a corporate LAN thereby providing convenient Internet and wide area network (VVAN) connectivity for the business customer. The business gateway 142′ will also enable a network provider to provision “frame-relay” data services at the customer's site. The business gateway 142′ can support symmetrical interface speeds of 10 Mbps and higher.
Finally, the CPE 110′ facilitates the transmission of various types of video services to the business user. The video services primarily includes distance learning and video conferencing. However, in addition, the business CPE 110′ can include ISDN BRI interfaces capable of supporting conventional video conferencing equipment. Using these interfaces, the business users will have the option of either viewing or hosting distance learning sessions at the business site building 144′.
Due to the proximity of the CPE 1432 to the CPE 1420, the ODU 1422 might receive transmissions from the ODU 1432. This would especially be possible if the signal strength of the transmission 1450 from ODU 1432 is stronger than the signal strength of the transmission 1440 from the base station 1410. For this reason, it is advantageous for the CPE 1420 to only measure power detectors in the receive pathway during a time when only the base station 1410 is transmitting user data.
The communication system uses the known reception time of the Mega Control message to address this problem. Each Mega Control message is timed so that the first byte of the message is received by the ODU at a time that is set aside in each TDD frame for base station downlink transmissions. Thus, when the ODU receives the first byte of the Mega Control message, it can measure the receive path power detectors and be assured that the only transmissions at that time are from a base station.
The system is designed such that under normal operation, a Mega Control Message (see Table 12) is sent along a broadband transmission cable (not shown) from the IDU 1424 to the ODU 1422 via FSK modulated signals. The Mega Control Message, as described above, is used by the IDU to control sub-components, such as VVA's, in the ODU. For this reason, the Mega Control Message is sent repeatedly, very frequently, and for the duration of the normal operation. The ODU responds to the Mega Control Message with the Mega Response Message (see Table 13) that includes settings of the detectors in the ODU.
As shown in the
At the front of each frame, and following the previous frame's transition gap, is a dedicated downlink time. In this embodiment, the minimum downlink time lasts 16.25 microseconds. Of course, the invention is not limited to any particular minimum downlink time. The minimum downlink time is used by the system to allow the base station to transmits internal command data to each of the CPEs. This command data, for example, can include the uplink/dowlink times for the next time frame. As discussed herein, the downlink time is only required to be long enough for the detectors to make a measurement from the detectors. Downlink times that are greater or lesser in duration are thus within the scope of the invention.
Thus, during this time only the base station is communicating with each CPE. The CPEs do not transmit during the minimum downlink time since they are receiving their instructions for the next frame. Because each time frame is of a fixed duration in the TDD system, and the minimum downlink time occurs at a fixed place (e.g.: at the end) of the frame in this embodiment, the IDU 1424 in the CPE 1420 knows that power measurements taken by the receive detectors during the minimum downlink time are guaranteed to only measure transmissions from the base station 1410.
In one embodiment of the system the micro controller 400 (
In one embodiment, the FSK modem in the IDU transmits data to the ODU at 115.2 kbps. With this link speed it takes 8.68 microseconds to transmit a single bit of data from the IDU to the ODU. Assuming eight data bits, one start bit and one stop bit, one byte of data can be transmitted from the IDU to the ODU in 86.8 microseconds. If a parity bit is included, the byte of data is transmitted in 8.68×11=95.48 microseconds.
For this reason, if the IDU is programmed to begin sending the Mega Control Message 86.8 microseconds before the beginning of the 16.25 microsecond downlink time, the first complete byte of the message will be received at the start of the downlink lime. If the micro controller 400 in the ODU is polling a UART or other buffer in the ODU to determine when the first byte of the message has been received from the IDU, it will be determine that the first byte has been received in the UART 166 at the start of the minimum downlink time.
Once a determination is made of the proper time to begin sending a Mega control message, the process 1600 moves to a state 1610 wherein software instructions within the IDU begin to build a Mega Control message. Once the mega control message has been built, it is handed to the FPGA 136. The FPGA 136 is aware of the frame timing and is programmed with an offset time, relative to the start of the frame, at which time the control message should be sent. The process 1600 then moves to a decision state 1612 to determine whether it is the proper time to begin sending the message. If a determination is made that it is the proper time to begin transmitting bits of the message from the IDU to the ODU, the process 1600 moves to a state 1616 wherein the bits comprising the message are handed to the hardware of the IDU in order to be transmitted to the ODU.
Once the IDU begins streaming bits from the mega control message to the ODU, the process 1600 moves to a state 1620 wherein a mega response message is received from the ODU. As can be appreciated, the mega response message includes the values that are read from the detectors in the ODU. After the mega response message has been received, the process 1600 moves to a state 1622 wherein the detector measurements stored within the mega response message are read by instructions stored within the IDU. As can be appreciated, these detector measurements are then used to determine whether adjustments need to be made to subcomponents of the ODU in order to more specifically receive, or transmit, user data with the highest efficiency. The process 1600 then terminates at an end state 1624.
If a determination had been made at the decision state 1612 that it was not the proper time to send a mega control message from the IDU to the ODU, the process 1600 moves to a wait state 1628 before returning to the decision state 1612. Thus, this loop continues until the IDU determines it is the proper time to begin transmitting bits to the ODU.
Referring now to
Once the detector readings have been taken at the state 1717, the process 1700 moves to a state 1720 wherein the mega response message is built by instructions within the FLASH memory of ODU. These instructions then transmit the mega response message to the IDU at a state 1724. The process 1700 then terminates at an end state 1730.
Of course it should be realized that embodiments of the invention are not limited to any particular TDD frame timing or number of time slots within each frame. For example, while each TDD time frame might be 1 millisecond in duration, the TDD time frame might alternatively be 0.5, 2, 5, 7, 10, 12, 15 or more milliseconds of duration. Moreover, each frame might be divided into any number of time slots. For example, each frame might be divided into 500 to 10000 time slots.
Moreover, the location and duration of the minimum downlink time is not limited to the embodiment described in FIG. 14. For example, the downlink time does not need to be located at the beginning of each frame. In one alternate embodiment, the minimum downlink time is located at the end or middle of each frame. The only requirement being that the minimum downlink time be fixed in relation to each frame so that the mega control message can be timed so that the first byte of the message is received by the ODU at the beginning of the minimum downlink time slot.
Accordingly, it is to be understood that the invention is not to be limited by the specific illustrated embodiment, but only by the scope of the appended claims.