Error Correction Control Services

bs/arq - ARQ Control

The functions in this service are used to set parameters of Automatic Repeat reQuest (ARQ) which is one of the MAC level data connection's error control mechanisms used by the basestation.

The arq service has the following functions:

<service name="bs/arq">
  <info>Set ARQ parameters</info>
  <args>
    <arg name="ackproctime" isRequired="false" value="[ackproctime]">
      <info>ACK proc time [] (0)</info>
    </arg>
    <arg name="blockltm" isRequired="false" value="[blockltm]">
      <info>ARQ block lifetime [] (5000)</info>
    </arg>
    <arg name="txackdelay" isRequired="false" value="[txackdelay]">
      <info>Tx ACK delay [] (100)</info>
    </arg>
    <arg name="sltmo" isRequired="false" value="[sltmo]">
      <info>Sync loss timeout [] (10000)</info>
    </arg>
    <arg name="dlvrorder" isRequired="false" value="[dlvrorder]">
      <info>Delivery in order: true/false (true)</info>
    </arg>
    <arg name="wsize" isRequired="false" value="[wsize]">
      <info>ARQ window size [0..1024] (1024)</info>
    </arg>
    <arg name="rxpurgetmo" isRequired="false" value="[rxpurgetmo]">
      <info>RX purge timeout [] (5000)</info>
    </arg>
    <arg name="enable" isRequired="false" value="[enable]">
      <info>Enable ARQ: true/false (false)</info>
    </arg>
    <arg name="rtmotx" isRequired="false" value="[rtmotx]">
      <info>TX retry timeout [] (1000)</info>
    </arg>
    <arg name="bloksize" isRequired="false" value="[blocksize]">
      <info>ARQ block size [0..(ARQ windows size/2)] (256)</info>
    </arg>
    <arg name="rtmorx" isRequired="false" value="[rtmorx]">
      <info>RX retry timeout [] (1000)</info>
    </arg>
  </args>
</service>

Arguments to /arq service are:

ackproctime

ACK proc time.

blockltm

ARQ block lifetime. This is the maximum time interval an ARQ block shall be managed by te transmitter ARQ state machine, once initial transmission of the block has occurred. If transmission (or subsequent retransmission) of the block is not acknowledged by the receiver before the time limit is reach, the block is discarded. Units: 100us. Allowed values: (0..65535)

txackdelay

Tx ACK delay. This is the time delay before receiver sends of an acknowledgement. Default: 100.

sltmo

Sync loss timeout. This is the maximum time interval ARQ_TX_WINDOW_START or ARQ_RX WINDOW_START parameters can stay at the same value before declaring a loss of synchronization between transmitter and receiver.

dlvrorder

Deliver in order on/off. This option tells received to forward SDUs in same order as sent by transmitter. Default: on

wsize

Transmission window size. This is the number of queued ARQ acknowledgement blocks at any given time for a connection. Default: 1024.

rxpurgetmo

RX purge timeout. This is the time interval the receiver shall wait after successful reception of a block that does not result in advancement of ARQ_RX_WINDOW_START value, before advancing to a new ARQ_RX_WINDOW_START.

enable

Indicates if ARQ is enabled for connection. Default: false.
NOTE: HARQ pdusn must be turned off if ARQ is enabled!

rtmotx

TX retry timeout. The minimum time interval a transmitter shall wait before retransmission of an unacknowledged block for retransmission. The interval begins when the ARQ block was last transmitted. Units: 100us. Allowed values: (0..65535)

bloksize

ARQ block size in bytes. Before transmission each SDU block is partitioned into a sequence of ARQ blocks of this size. Allowed values are powers of two ranging from 16 to 1024 bytes, e.g. 16, 32, 64 and so on. Default: 1024.

NB: Even if a large block size or window size is permitted by the base station, the client may still negotiate something smaller. (As we have seen on a Linux client with the Intel 6250 card.)

rtmorx

RX retry timeout. Units: 100us. Allowed values: (0..65535)

bs/harq - HARQ Control

Service for controlling Hybrid Automatic Repeat reQuest (HARQ) parameters. With HARQ, in addition to ARQ error detection, blocks of data are FEC encoded before transmission. This service has the following arguments:

<service name="bs/harq">
  <info>Set HARQ parameters</info>
  <args>
    <arg name="mimoul" isRequired="false" value="[mimoul]">
      <info>MIMO HARQ support: true/false (IGNORED - mimo support not available for this BS)</info>
    </arg>
    <arg name="pdusn" isRequired="false" value="[pdusn]">
      <info>PDU SN extended subheader reordering enabled: true/false (true)</info>
    </arg>
    <arg name="mret" isRequired="false" value="[retran]">
      <info>Maximum number of retransmissions [0..255] (4)</info>
    </arg>
    <arg name="burst" isRequired="false" value="[burst]">
      <info>Maximum number of HARQ bursts per frame [0..255] (17)</info>
    </arg>
    <arg name="enable" isRequired="false" value="[enable]">
      <info>Enable HARQ: true/false (false)</info>
    </arg>
    <arg name="uldelay" isRequired="false" value="[uldelay]">
      <info>Frame offset of UL ACK delay wrt to UL Burst [2,3] (3)</info>
    </arg>
    <arg name="dldelay" isRequired="false" value="[dldelay]">
      <info>Frame offset of DL ACK delay wrt to DL Burst [1,2,3] (1)</info>
    </arg>
  </args>
</service>

enable

Indicates if HARQ is enabled for connection. Default: false Note: Permuation mode must be PUSC if HARQ is enabled (permuation —> 0)

pdusn

Indicates if PDU SN extended sub-header reordering is enabled. Default: true. This must be disabled if ARQ is turned on.
NOTE: Intel 5150/6250 clients need this feature turned off if harq is enabled!

mret

Maximum number of retransmissions. Range = [0,255], Default: 4

burst

Maximum number of HARQ bursts per frame. Range: [0,255], Default: 17

mimoul

Indicates if MIMO HARQ support is enabled. (IGNORED - mimo support not available for this BS)

dldelay

Frame offset of DL ACK delay with respect to DL Burst. Range: [1,3], Default: 1

uldelay

Frame offset of UL ACK delay with respect to UL Burst. Range: [2,3], Default: 3

References

1. ​http://wiki.hsc.com/wiki/Main/WimaxArq
2. ​http://www.simet.com.tr/documents/product/F83D610A-B7F6-ADBD-907AB9D8F8708319.pdf
3. Performance Analysis of the IEEE 802.16 ARQ Mechanism. Sayenko, Tykhomyrov, Martikainen, Alanen.