WO2001022747A1 - Selecting channels for retransmission of data packets - Google Patents

Selecting channels for retransmission of data packets Download PDF

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Publication number
WO2001022747A1
WO2001022747A1 PCT/US2000/024021 US0024021W WO0122747A1 WO 2001022747 A1 WO2001022747 A1 WO 2001022747A1 US 0024021 W US0024021 W US 0024021W WO 0122747 A1 WO0122747 A1 WO 0122747A1
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Prior art keywords
data
retransmission
channel
packet
channels
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PCT/US2000/024021
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French (fr)
Inventor
John M. Harris
Robert T. Love
Joseph M. Pettinger
Matthew F. Valentine
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Motorola Inc.
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Publication of WO2001022747A1 publication Critical patent/WO2001022747A1/en

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    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04WWIRELESS COMMUNICATION NETWORKS
    • H04W28/00Network traffic management; Network resource management
    • H04W28/16Central resource management; Negotiation of resources or communication parameters, e.g. negotiating bandwidth or QoS [Quality of Service]
    • H04W28/18Negotiating wireless communication parameters

Definitions

  • the invention relates to the field of communications, and more particularly, to efficient channel utilization in communication systems.
  • Communication systems such as the commonly known code division multiple access (CDMA) 2000 which is the next generation of the commonly known system based on IS-95 CDMA standard, or wide-band CDMA ( -CDMA) which is the next generation of the commonly known system based on the Global System Mobile (GSM) standards, include down-link communication to a number of mobile stations via fundamental and supplemental channels. Other types of down link channels, such as paging channels or synchronization channels, may also be present.
  • a base station may use the fundamental and supplemental " channels to transmit data to a mobile station. " Each base station may have access to at least one of several supplemental channels and one fundamental channel, depending on the type of system and its requirements.
  • the informations communicated in each channel are coded according to an orthogonal code selected from, for example, the Walsh codes.
  • a fundamental channel is typically used for voice communications, however, it may also be used for low bit rate data communications. Supplemental channels, typically, are used for data communications.
  • a data transmit session between a mobile station and a base station may last as long as all the data in a block of data are transmitted to the mobile station.
  • a block of data may be partitioned into a series of packets of data where each packet would have a serial or sequence number identifying the location of the packet in the block of data.
  • Each packet may be transmitted over a burst to the mobile station. After each burst of data is received at a mobile station, the mobile station is required to measure quality of the received data. If the measured quality, such as number of errors in the burst, does not match a predetermined threshold, the mobile station after detecting reception failure transmits to the base station a negative acknowledgement (NAK) message indicating inadequate reception quality. The base station, in proper time, retransmits the burst of data.
  • NAK negative acknowledgement
  • the base station retransmits only the packet of data that has been identified in the NAK message.
  • the base station may select the time for transmission of the NAK packet of data.
  • the retransmitted packet of data has the same serial number even though it is retransmitted out of order along with other remaining packets of data.
  • a data block may be partitioned into 50 packets of data, numbered from 1 to 50 consecutively.
  • the base station begins transmitting the packets of data, starting with the first packet, on at least one of the supplemental channels or the fundamental channels if the fundamental channel is free.
  • a block of data 101 is partitioned into a number of data packets 110.
  • the first packet has the serial number 1, and the second packet the serial number 2, and so on.
  • the first packet is transmitted on a first supplemental (SI) channel 111
  • the second data packet on a second supplemental (S2) channel 112
  • the third packet is transmitted on a third supplemental (S3) channel 113.
  • the base station typically is not limited to a selection of the supplemental channels.
  • a base station has access to all supplemental and the fundamental channels for transmitting a block of data on a series of bursts of data. The scenario shown in FIG. 1, although shows only three supplemental channels in use, is for illustration purpose only.
  • the receiving unit 190 after comparing quality of received data packet 2, retransmission of data packet 2 (R2), data packet 8, data packet 20, and data packet R8 may transmit a number of NAK messages to the base station after detecting each reception failure.
  • the NAK messages in this example, have been associated with supplemental channels 111 and 112 while every data packets transmitted on supplemental channel 113 have been received without any problem.
  • data packet 2 has been retransmitted twice and data packet 8 once without adequate reception at the receiver 190.
  • FIG. 1 depicts a data packet flow for transmission of a data block according to the prior art.
  • FIG. 2 depicts a data packet flow for transmission of a data block according to various aspects of the invention by including a comparator before selecting which channel is to be used for retransmission of a failed packet of data.
  • a method in a communication system, includes receiving a negative acknowledgement message from a remote unit, such as a mobile station, indicating reception failure of a packet of data.
  • a remote unit such as a mobile station
  • a link quality of a plurality of channels available for transmission By comparing a link quality of a plurality of channels available for transmission, at least one of the plurality of channels is selected based on the comparison. The selected channel is then used for retransmission of the packet of data. Accordingly, the retransmission of the failed packet of data has a better " chance of being received at the remote unit since the selected channel may have a better link quality than the channel that was originally used for transmission. If there is any subsequent retransmission, the method is repeated.
  • the quality of a channel may be determined based on at least one of frame erasure ratio, channel noise, cyclic redundancy check information, average energy to interference ratio, signal to noise ratio, and power level of the plurality of channels. Other qualities of measurements are also possible.
  • the plurality of retransmission packets of data are sorted according to a sequence number associated with each of the plurality of retransmission packets of data. Each packet of retransmission data is assigned a priority for retransmission.
  • the available channels include a fundamental channel and at least a supplemental channel
  • the fundamental channel may be selected for retransmission of a retransmission packet of data that has a highest priority according to the selected priority.
  • FIG. 2 Similar to the flow " shown in FIG. 1, there are several packets of data that have failed to be received at the receiver 190. For example, the data packet 2 transmitted on supplemental channel 112 failed to be received at the receiver 190.
  • the base station at a comparator 201 compares link quality of all available channels 210 for retransmission of data packet 2. There may be a number of available channels for retransmission. Comparator 201 may be implemented via software or hardware. Such implementation is widely known by one ordinary skilled in the art. In this example, when the R2 is being sent, channel 113, i.e.
  • supplemental channel S3 appears to have the best quality. Retransmission of data block R2 on channel 113 has statistically a better chance of being received than being retransmitted on, for example, channel 112. In case of R8 , and R20, the channel 112 clearly, in this example, has poor quality, thus sending R2 and R8 on channels 111 or 112 would make an inefficient use of the available channels for retransmission.
  • multiple Walsh codes are used for each data call. For each High Speed Data (HSD) call the primary Walsh code is called the fundamental and the other " alsh codes are called the supplemental. The number of supplemental is generally between 0 and 7. Only the fundamental channel carries the power control information and the IS-95 system messaging.
  • RLP radio link protocol
  • Fundamental Channel essentially is used for voice, low bit rate data, and signaling at either 9.6Kbps or 14.4Kbps.
  • Supplemental Channel is mainly used for high bit rate data and multimedia applications.
  • Dedicated Control Channel is used for the control and signaling purpose.
  • RLP Radio Link Protocol
  • TCP/IP will 'time-out.' When TCP/IP times-out it takes approximates 2 to 3 seconds for the corrupted packets to be retransmitted. This is a significant delay and thus number of aborts should be minimized. However, as the FER increase, so does the probability of an RLP abort. Generally, system messaging and power control information needs to be transmitted through a radio link with a low FER (e.g. near 1%) .
  • the fundamental channel unlike the supplemental channels is punctured to allow for power control information. This results in the fundamental channel having a higher FER than the supplemental channels for a given set of power control parameters. Thus, it is necessary to use different power control parameters on the fundamental and the supplemental channels in IS-95 independent of the other issues.
  • the fundamental channel FER target should be similar to that used " for voice; between 1% and 3%. This will ensire that the messaging on the fundamental channel will pass through a sufficiently reliable link (when the cell is not overloaded.)
  • the supplemental channel FER target should be higher than what is used for voice; between 3% and 10%. This is because data call use RLP to correct errors on the radio link.
  • By using a higher FER target for the data supplemental one can drastically reduce the capacity impact of data calls. This is because a call with a higher FER requires less power and thus causes less interference. For example, cell capacity is 40% larger for a system where data calls have 5% FER targets and can tolerate a maximum of 10% FER than the capacity of a cell with voice calls with a 1% target which can tolerate a maximum of 2% FER.
  • the RLP retransmissions may be preferentially placed on the fundamental (or Dedicated Control Channel in CDMA 2000) when being transmitted.
  • the algorithm should send the retransmission.
  • This prioritization is implemented by using a sorting algorithm on the output of the RLP algorithm " .
  • the implementation of this sorting algorithm can use the fact that in RLP each frame contains a flag that identifies the frame as a retransmission frame or an original frame.
  • the best sorting algorithm choice would not only give the retransmissions higher priority than original transmissions on the fundamental (or Dedicated Control Channel in CDMA 2000), it would also give the oldest retransmissions the highest priority on the fundamental (or Dedicated Control Channel in CDMA 2000) .
  • the sorting algorithm may be according: Scan through each of the frames, find the frame with the smallest sequence number and place it on the fundamental (or Dedicated Control Channel in CDMA 2000) . As a result, each frame in RLP is given a sequence number. While a frame is being retransmitted, the current sequence number of the— successful frames continues to increase. When the- retransmission is attempted, its sequence number is much smaller that the current sequence number. Only 3 sets of attempts are made by RLP to send each frame. For the same reasoning, the retransmission with the smallest sequence number is the oldest, and thus has the smallest number of retransmission attempts left before RLP will 'give up' and abort it.
  • TCP/IP will 'time-out.' When TCP/IP times-out it takes approximates 2 to 3 seconds for the corrupted packets to be resent. This is a significant delay and thus number of aborts should be minimized. This algorithm does that by reducing the number of and probability of aborts by 99.4%. This corresponds to having an abort every 422 Minutes instead of every 1207 hours, instead of every 7 hours.
  • RLP sequence number based sorting algorithm for distinguishing which frames are sent on the fundamental has substantial benefit in retransmission efficiency. Moreover, utilizing the lower FER on fundamental to satisfy signaling and power control requirements while to significantly improving RLP performance, and utilizing higher FER on supplemental to obtain significant capacity benefits data traffic.

Abstract

In a communication system, a method and apparatus includes receiving a negative acknowledgement message from a remote unit (190) indicating reception failure of a packet of data. By comparing at a comparator (201) a link quality of a plurality of available channels (210) for transmission, at least one of the plurality of channels is selected based on the comparison. The selected channel is then used for retransmission of the packet of data. Accordingly, the retransmission of the failed packet of data has a better chance of being received at the remote unit since the selected channel may have a better link quality than the channel that was originally used for transmission. If there is any subsequent retransmission, the method is repeated.

Description

SELECTING CHANNELS FOR RETRANSMISSION OF DATA PACKETS
Related Field of the Invention
The invention relates to the field of communications, and more particularly, to efficient channel utilization in communication systems.
Background of the Invention
Communication systems, such as the commonly known code division multiple access (CDMA) 2000 which is the next generation of the commonly known system based on IS-95 CDMA standard, or wide-band CDMA ( -CDMA) which is the next generation of the commonly known system based on the Global System Mobile (GSM) standards, include down-link communication to a number of mobile stations via fundamental and supplemental channels. Other types of down link channels, such as paging channels or synchronization channels, may also be present. A base station may use the fundamental and supplemental "channels to transmit data to a mobile station. "Each base station may have access to at least one of several supplemental channels and one fundamental channel, depending on the type of system and its requirements. The informations communicated in each channel are coded according to an orthogonal code selected from, for example, the Walsh codes. A fundamental channel is typically used for voice communications, however, it may also be used for low bit rate data communications. Supplemental channels, typically, are used for data communications.
A data transmit session between a mobile station and a base station may last as long as all the data in a block of data are transmitted to the mobile station. A block of data may be partitioned into a series of packets of data where each packet would have a serial or sequence number identifying the location of the packet in the block of data. Each packet may be transmitted over a burst to the mobile station. After each burst of data is received at a mobile station, the mobile station is required to measure quality of the received data. If the measured quality, such as number of errors in the burst, does not match a predetermined threshold, the mobile station after detecting reception failure transmits to the base station a negative acknowledgement (NAK) message indicating inadequate reception quality. The base station, in proper time, retransmits the burst of data.
In case of a NAK condition, the base station retransmits only the packet of data that has been identified in the NAK message. The base station may select the time for transmission of the NAK packet of data. There may be more than one packet of data in a • queue for retransmission. The retransmitted packet of data has the same serial number even though it is retransmitted out of order along with other remaining packets of data. For example, a data block may be partitioned into 50 packets of data, numbered from 1 to 50 consecutively. The base station begins transmitting the packets of data, starting with the first packet, on at least one of the supplemental channels or the fundamental channels if the fundamental channel is free.
Data transmission and retransmission may be more apparent by making references to the FIG. 1. A block of data 101 is partitioned into a number of data packets 110. The first packet has the serial number 1, and the second packet the serial number 2, and so on. As an example, "the first packet is transmitted on a first supplemental (SI) channel 111, the second data packet on a second supplemental (S2) channel 112, and the third packet is transmitted on a third supplemental (S3) channel 113. The base station typically is not limited to a selection of the supplemental channels. A base station has access to all supplemental and the fundamental channels for transmitting a block of data on a series of bursts of data. The scenario shown in FIG. 1, although shows only three supplemental channels in use, is for illustration purpose only. The receiving unit 190 after comparing quality of received data packet 2, retransmission of data packet 2 (R2), data packet 8, data packet 20, and data packet R8 may transmit a number of NAK messages to the base station after detecting each reception failure. Note, the NAK messages, in this example, have been associated with supplemental channels 111 and 112 while every data packets transmitted on supplemental channel 113 have been received without any problem. Moreover, note that data packet 2 has been retransmitted twice and data packet 8 once without adequate reception at the receiver 190.
Therefore, there is a need for a method and apparatus"" for selecting channels for retransmission of data packets in a communication system. Brief Description of the Drawings FIG. 1 depicts a data packet flow for transmission of a data block according to the prior art.
FIG. 2 depicts a data packet flow for transmission of a data block according to various aspects of the invention by including a comparator before selecting which channel is to be used for retransmission of a failed packet of data.
Detailed Description of the Preferred Embodiment (s) According to various aspects of the invention, in a communication system, a method includes receiving a negative acknowledgement message from a remote unit, such as a mobile station, indicating reception failure of a packet of data. By comparing a link quality of a plurality of channels available for transmission, at least one of the plurality of channels is selected based on the comparison. The selected channel is then used for retransmission of the packet of data. Accordingly, the retransmission of the failed packet of data has a better " chance of being received at the remote unit since the selected channel may have a better link quality than the channel that was originally used for transmission. If there is any subsequent retransmission, the method is repeated.
According to various aspects of the invention, the quality of a channel may be determined based on at least one of frame erasure ratio, channel noise, cyclic redundancy check information, average energy to interference ratio, signal to noise ratio, and power level of the plurality of channels. Other qualities of measurements are also possible. In case there is more than one packet of data for retransmission, the plurality of retransmission packets of data are sorted according to a sequence number associated with each of the plurality of retransmission packets of data. Each packet of retransmission data is assigned a priority for retransmission. Where the available channels include a fundamental channel and at least a supplemental channel, the fundamental channel may be selected for retransmission of a retransmission packet of data that has a highest priority according to the selected priority.
Various aspects of the invention may be more apparent by making references to the FIG. 2. Similar to the flow "shown in FIG. 1, there are several packets of data that have failed to be received at the receiver 190. For example, the data packet 2 transmitted on supplemental channel 112 failed to be received at the receiver 190. When a retransmission of the data packet (R2) is about to take place, the base station at a comparator 201 compares link quality of all available channels 210 for retransmission of data packet 2. There may be a number of available channels for retransmission. Comparator 201 may be implemented via software or hardware. Such implementation is widely known by one ordinary skilled in the art. In this example, when the R2 is being sent, channel 113, i.e. supplemental channel S3, appears to have the best quality. Retransmission of data block R2 on channel 113 has statistically a better chance of being received than being retransmitted on, for example, channel 112. In case of R8 , and R20, the channel 112 clearly, in this example, has poor quality, thus sending R2 and R8 on channels 111 or 112 would make an inefficient use of the available channels for retransmission. In IS-95B systems, multiple Walsh codes are used for each data call. For each High Speed Data (HSD) call the primary Walsh code is called the fundamental and the other" alsh codes are called the supplemental. The number of supplemental is generally between 0 and 7. Only the fundamental channel carries the power control information and the IS-95 system messaging. In cdma2000, three different channels may be used for transmission of radio link protocol (RLP) frames that may include error messages such as NAK messages. Such channels include:
1) Fundamental Channel essentially is used for voice, low bit rate data, and signaling at either 9.6Kbps or 14.4Kbps. 2) Supplemental Channel is mainly used for high bit rate data and multimedia applications. 3) Dedicated Control Channel is used for the control and signaling purpose.
In IS-95, CDMA 2000 and CDMA One, data calls use Radio Link Protocol (RLP) to correct errors on the radio link. RLP attempts to correct all radio errors using the following algorithm. Consider a new frame before it is transmitted across the radio link for the first time. If this frame is 'erased' by the radio link, the RLP requests two more copies of it to be retransmitted. If neither of these arrive, then RLP requests 3 more copies. If none of the packets arrive successfully, then RLP gives up and the packet which the frame was a part of is corrupted and must be retransmitted by TCP/IP or a higher level protocol. When RLP gives up in this fashion, the action may be 'aborted'. If two or more TCP/IP packets in a row contain at least one frame each which has been aborted, then TCP/IP will 'time-out.' When TCP/IP times-out it takes approximates 2 to 3 seconds for the corrupted packets to be retransmitted. This is a significant delay and thus number of aborts should be minimized. However, as the FER increase, so does the probability of an RLP abort. Generally, system messaging and power control information needs to be transmitted through a radio link with a low FER (e.g. near 1%) .
In IS-95B the fundamental channel unlike the supplemental channels is punctured to allow for power control information. This results in the fundamental channel having a higher FER than the supplemental channels for a given set of power control parameters. Thus, it is necessary to use different power control parameters on the fundamental and the supplemental channels in IS-95 independent of the other issues.
The fundamental channel FER target should be similar to that used" for voice; between 1% and 3%. This will ensire that the messaging on the fundamental channel will pass through a sufficiently reliable link (when the cell is not overloaded.) The supplemental channel FER target should be higher than what is used for voice; between 3% and 10%. This is because data call use RLP to correct errors on the radio link. By using a higher FER target for the data supplemental, one can drastically reduce the capacity impact of data calls. This is because a call with a higher FER requires less power and thus causes less interference. For example, cell capacity is 40% larger for a system where data calls have 5% FER targets and can tolerate a maximum of 10% FER than the capacity of a cell with voice calls with a 1% target which can tolerate a maximum of 2% FER.
The RLP retransmissions (frames which were in error and must be retransmitted) may be preferentially placed on the fundamental (or Dedicated Control Channel in CDMA 2000) when being transmitted. In other words, when given a choice between sending a retransmission or a new frame on the fundamental (or Dedicated Control Channel in CDMA 2000), the algorithm should send the retransmission. This prioritization is implemented by using a sorting algorithm on the output of the RLP algorithm". The implementation of this sorting algorithm can use the fact that in RLP each frame contains a flag that identifies the frame as a retransmission frame or an original frame.
Figure imgf000012_0001
The best sorting algorithm choice would not only give the retransmissions higher priority than original transmissions on the fundamental (or Dedicated Control Channel in CDMA 2000), it would also give the oldest retransmissions the highest priority on the fundamental (or Dedicated Control Channel in CDMA 2000) . The sorting algorithm may be according: Scan through each of the frames, find the frame with the smallest sequence number and place it on the fundamental (or Dedicated Control Channel in CDMA 2000) . As a result, each frame in RLP is given a sequence number. While a frame is being retransmitted, the current sequence number of the— successful frames continues to increase. When the- retransmission is attempted, its sequence number is much smaller that the current sequence number. Only 3 sets of attempts are made by RLP to send each frame. For the same reasoning, the retransmission with the smallest sequence number is the oldest, and thus has the smallest number of retransmission attempts left before RLP will 'give up' and abort it.
In short, it is more important to send a third & final round retransmission across the radio link successfully than it is to send a first or second set of attempts successfully because if the third attempt is the final attempt.
F irst A ttem pt to S end F 1 Original Transm ission of Fram e F l with Sequence N um ber 1
F2
Figure imgf000013_0001
If all three sets of transm issions/retransm ission of Fram e 1 fail then the fram e is aborted and the corrupted packet is was a part of is given to TCP/IP to retransm it
The idea of sending three retransmissions on the third and f nal attempt in RLP is an attempt at achieving- the same goal of giving the final transmission attempt a higher probability of success Table 1 shows the use of the algorithm provides a 99.4% decrease in aborts. If RLP aborts, then it gives up and the packet that the frame was a part of is corrupted and must be retransmitted by TCP/IP. When RLP gives up in this fashion, it has 'aborted'. If two or more TCP/IP packets in a row contain at least one frame each which has been aborted, then TCP/IP will 'time-out.' When TCP/IP times-out it takes approximates 2 to 3 seconds for the corrupted packets to be resent. This is a significant delay and thus number of aborts should be minimized. This algorithm does that by reducing the number of and probability of aborts by 99.4%. This corresponds to having an abort every 422 Minutes instead of every 1207 hours, instead of every 7 hours.
Figure imgf000015_0001
Table 1: Benefits of Prioritizing Oldest Retransmissions
The impact of this algorithm on delay is also positive. The delay variance decreases by 3% and the mean delay decrease by 0.4%. This will result in smaller buffer requirements in RLP and mobile. The fact that the delay mean goes down .4% and the
10 throughput goes down 0.1% should result in an overall performance improvement. For example, for a 1500 byte TCP-IP Parcket, the delay decrease of 0.4% will reduce the RLP delay by 0.7 milliseconds, and the throughput increase of 0.1% will increase the delay by 0.2 milliseconds. Thus, the overall delay change seen by a TCP/IP packet is a decrease of 0.5 milliseconds.
Accordingly, RLP sequence number based sorting algorithm for distinguishing which frames are sent on the fundamental has substantial benefit in retransmission efficiency. Moreover, utilizing the lower FER on fundamental to satisfy signaling and power control requirements while to significantly improving RLP performance, and utilizing higher FER on supplemental to obtain significant capacity benefits data traffic.

Claims

Claims
1. In a communication system, a method comprising the steps of: receiving a negative acknowledgement message from a remote unit indicating reception failure of a packet of data at said remote unit; comparing a link quality of a plurality of channels available for transmission; selecting at least one of said plurality of channels based on said comparing; using said selected channel for retransmission of said packet of data.
2. The method as recited in claim 1 wherein said comparing comprising: determining said quality based on at least one of frame erasure ratio, channel noise, cyclic redundancy check information, average energy to interference ratio, signal to noise ratio, and power level of said plurality of channels.
3. The -method "as recited in claim 1 further comprising: sorting a plurality of retransmission packets of data according to a sequence number associated with each of said plurality of retransmission packets of data, and selecting a priority for said sorted plurality of packets of data for retransmission.
4. The method as recited in claim 3 wherein said available channels include a fundamental channel and at least a supplemental channel, further comprising selecting said fundamental channel for retransmission of a highest priority retransmission packet of data according to said priority.
5. In a communication system, an apparatus comprising: means for receiving a negative acknowledgement message from a remote unit indicating reception failure of a packet of data at said remote unit; means for comparing a link quality of a plurality of channels available for transmission; means for selecting at least one of said plurality of channels based on" said comparing; means for using said selected channel for retransmission of said packet of data.
6. The apparatus as recited in claim 5 wherein said means for comparing comprising: means for determining said quality is based on at least one of frame erasure ratio, channel noise, cyclic redundancy check information, average energy to interference ratio, signal to noise ratio, and power level of said plurality of channels.
7. The apparatus as recited in claim 5 further comprising: means for sorting a plurality of retransmission packets of data according to a sequence number associated with each of said plurality of retransmission packets of data, and means for selecting a priority for said sorted plurality of packets of data for retransmission.
8. The apparatus as recited in claim 7 wherein said available channels include a fundamental channel and at least a supplemental channel, further comprising means for selecting said fundamental channel for retransmission of a highest priority retransmission packet of' data according to said priority.
PCT/US2000/024021 1999-09-22 2000-08-31 Selecting channels for retransmission of data packets WO2001022747A1 (en)

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US6088342A (en) * 1997-05-05 2000-07-11 Nokia Mobile Phones Limited Dynamic configuration of radio link protocol in a telecommunications system
US6021124A (en) * 1997-08-19 2000-02-01 Telefonaktiebolaget Lm Ericsson Multi-channel automatic retransmission query (ARQ) method

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1540866B1 (en) * 2002-08-16 2019-03-06 Google Technology Holdings LLC Method and apparatus for reliably communicating information packets in a wireless communication network
US8935588B2 (en) 2004-09-15 2015-01-13 Cellular Communications Equipment Llc Decoding method
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