 |
This chapter of TIA/EIA/IS-707 specifies procedures for the Radio Link Protocols supporting the CDMA data services. The Radio Link Protocol specified for the Rate Set 1 multiplex sublayer is a compatible superset of the previous specifications for RLP found in TIA/EIA/IS-99, and in TIA/EIA/IS-657. The Radio Link Protocol specified for the Rate Set 2 multiplex sublayer includes new frame definitions and new segmentation options.
The Radio Link Protocol (RLP) provides an octet stream transport service over forward and reverse traffic channels. RLP is unaware of higher layer framing; it operates on a featureless octet stream, delivering the octets in the order received.
The RLP may be either transparent or non-transparent. Transparent RLP provides maximum throughput transmission of service option data over a CDMA traffic channel, while maintaining bit count integrity over the air interface. The error rate for transparent RLP is that observed on the traffic channel itself. Typically this requires that upper layer data transmission protocols provide error recovery techniques equivalent to those provided in the non-transparent RLP.
Non-transparent RLP substantially reduces the error rate exhibited by
CDMA traffic channels. There is no direct relationship between upper
layer packets and the underlying traffic channel frames; a large packet
may span multiple traffic channel frames, or a single traffic channel
frame may contain all or part of several small upper layer packets.
Section 2 below is a general description of RLP that defines its use by
any service option for which it is suited. Section 3 defines the RLP
procedures for encrypted or non-encrypted applications. Section 4
defines the RLP frame formats.
For service options supporting an interface with Multiplex Option 1 or
with Multiplex Option 2, non-transparent RLP frames may be transported
as primary traffic, or as secondary traffic. Transparent RLP frames
shall only be transported as primary traffic.
Transparent RLP frames are transported as primary traffic, while
non-transparent RLP frames can be carried as any traffic type. Section
2.2.1 applies to both transparent and non-transparent RLP
frames. Section 2.2.2 applies to non-transparent RLP frames only.
When carried as primary traffic, the RLP shall generate and supply
exactly one frame containing the service option bits to the multiplex
sublayer every 20 milliseconds. The frame shall be one of the types as
shown in Table 2.2.1-1. The number of bits supplied to the multiplex
sublayer for each type of frame shall also be as shown in Table 2.2.1-1.
Unless otherwise commanded by Multiplex Option 1, RLP may supply a Rate
1, Rate 1/2, Rate 1/8 or Blank frame. Unless otherwise commanded by
Multiplex Option 2, RLP may supply a Rate 1, Rate 1/2, Rate 1/4, Rate
1/8 or Blank frame. Upon command, the RLP shall generate a Blank
frame. A Blank frame contains no bits and is used for burst transmission
of signaling traffic (see 6.1.3.3.11 of TSB74) or when the RLP is unable
to send a segment of a segmented data frame. Also upon command, the RLP
shall generate a non-blank frame with a maximum rate of Rate 1/2.
1.2 Terms
1.3 References
2 GENERAL REQUIREMENTS
2.1 Required Multiplex Option Support
2.2 Interface to Multiplex Options
2.2.1 Primary Traffic
|
Table 2.2.1-1. Primary Traffic Frame Types Supplied by the RLP to the Multiplex Sublayer
The multiplex sublayer in the mobile station categorizes every received Traffic Channel frame (see 6.2.2.2 of TSB74), and supplies the frame type and accompanying bits, if any, to the RLP. Table 2.2.1-2 lists the frame types supplied by the multiplex sublayer when RLP is carried as primary traffic by Multiplex Option 1. Although RLP does not generate Rate 1/4 frames, Multiplex Option 1 is not required to recognize this fact. RLP shall declare any received Rate 1/4 frames to be erasures. Table 2.2.1-3 lists the frame types supplied by the multiplex sublayer when RLP is carried as primary traffic by Multiplex Option 2.
|
Table 2.2.1-2. Primary Traffic Frame Types Supplied by the Multiplex Sublayer to the RLP for Multiplex Option 1
|
Table 2.2.1-3. Primary Traffic Frame Types Supplied by the Multiplex Sublayer to RLP for Multiplex Option 2
When carried as secondary traffic, RLP shall generate and supply one frame containing the service option bits to the multiplex sublayer every 20 milliseconds. The frame shall be one of the types shown in Table 2.2.2-1. The number of bits supplied to the multiplex sublayer for each type of frame shall also be as shown in Table 2.2.2-1. Upon command, the RLP shall generate a Blank frame. A Blank frame contains no bits and is used for burst transmission of signaling traffic (see 6.1.3.3.11 of TSB74), when primary traffic has priority over secondary traffic and the primary traffic service option sends a Rate 1 frame, or when the RLP is unable to send a segment of a segmented data frame (see 3.1.4).
|
Table 2.2.2-1. Secondary Traffic Frame Types Supplied by the RLP to the Multiplex Sublayer
The multiplex sublayer in the mobile station categorizes every received Traffic Channel frame (see 6.2.2.2 of TSB74) and supplies the frame type and accompanying bits, if any, to the RLP. Table 2.2.2-2 shows the frame types that may be sent to RLP by the multiplex sublayer when RLP is carried as secondary traffic using Multiplex Option 1. Table 2.2.2-3 shows the frame types that may be sent to RLP by the multiplex sublayer when RLP is carried as secondary traffic using Multiplex Option 2.
|
Table 2.2.2-2. Secondary Traffic Frame Types Supplied by the Multiplex Sublayer to RLP for Multiplex Option 1
|
Table 2.2.2-3. Secondary Traffic Frame Types Supplied by the Multiplex Sublayer to RLP for Multiplex Option 2
Each RLP layer shall classify the frames it sends into three priority
classes. In order of priority they are, with highest priority first:
When a service option using RLP is connected as primary traffic, and there is no service option connected as secondary traffic, the mobile station should observe the following priorities in using the traffic channel:
When a service option using RLP is connected as secondary traffic, and a service option not using RLP is connected as primary traffic, the mobile station should observe the following priorities in using the traffic channel, if the primary traffic service option permits:
When data from a service option using RLP over secondary traffic has a lower priority than data from the service option using primary traffic, the blank and burst with secondary traffic frame format (see 6.1.3.3 of TSB74) shall not be used unless the primary traffic service option has no data to send.
When service options using RLP are connected as both primary and secondary traffic, the mobile station should observe the following priorities in using the traffic channel:
When transparent RLP frames are carried as primary traffic, the following priorities should be observed by the mobile station when using the traffic channel.
Non-transparent RLP provides the capability of both non-encrypted mode and encrypted mode data transport. The encryption capability is selected during RLP Initialization/Reset and is accomplished as a negotiation between the mobile station and the BS/MSC. In addition, a procedure for synchronizing RLP without encryption negotiation is also provided here. The two techniques are compatible with each other and therefore can co-exist in systems where encryption negotiation is supported in the infrastructure equipment, but possibly not in some of the mobile stations attempting access to the system.
This standard defines two alternate RLP Initialization/Reset procedures. Non-Encrypted Mode initialization/reset shall be used by mobile stations and BS/MSCs that do not support RLP data frame encryption for the desired service. Encrypted Mode initialization/reset procedures shall be used by mobile stations and BS/MSCs to negotiate the use of RLP data frame encryption.
Non-transparent RLP is established with a bidirectional handshake, after
connection of the service option that uses RLP, to synchronize the
connection. To establish the RLP without data encryption all control
frames used (SYNC, ACK, and SYNC/ACK) shall conform to the Non-Encrypted
Mode RLP control frame definitions (see 4.3.1). Accordingly,
the control frame names referenced in this section refer only to the
Non-Encrypted Mode versions of these frames.
When a traffic type carrying RLP frames is activated, when the traffic
type carrying RLP frames is changed, and at other times as specified in
this standard or in other service option standards, the RLP layer shall
perform the initialization/reset procedure below.
When the RLP layer is initialized or reset, and when a SYNC RLP control
frame is received, the RLP layer shall perform the following:
When the RLP layer is initialized or reset, it shall transmit a
continuous stream of SYNC RLP control frames (see 4.3.1). When
the RLP layer receives a SYNC RLP control frame it shall respond with a
SYNC/ACK RLP control frame, and shall continue sending SYNC/ACK RLP
control frames until the next valid frame which is not a SYNC RLP
control frame is received. When the RLP layer receives a SYNC/ACK RLP
control frame it shall respond with an ACK RLP control frame, and shall
continue sending ACK RLP control frames until the next valid frame which
is not a SYNC/ACK control frame is received. When the RLP layer receives
an ACK RLP control frame, it shall send no more SYNC, SYNC/ACK or ACK
RLP control frames, and should begin sending RLP data frames.
When RLP frames are carried as primary or secondary traffic, the RLP
layer shall store in RLP_DELAYs the number of frames received
between the sending of the last SYNC or SYNC/ACK RLP control frame and
reception of the first valid frame that is not an ACK or SYNC/ACK RLP
control frame. RLP_DELAYs is used in NAK retransmission timing, as
described in 3.1.2.1.
CDMA mobile stations complying with this standard may support
authentication (see 6.3.12 of TIA/EIA/IS-95) and may support encryption
of RLP data frames using the procedures defined below. RLP data
encryption shall be performed whenever cellular authentication
procedures have been performed during the establishment of a CDMA
Traffic Channel and RLP data encryption is negotiated (see
3.1.1.2.2).
The RLP layer shall maintain a 30-bit extended sequence number
EXT_V(S). EXT_V(S) shall be set to zero when the RLP Layer is
initialized following the establishment of a Traffic Channel. For all
subsequent initializations/resets of the RLP Layer while the Traffic
Channel remains established, the RLP Layer shall perform the following
prior to sending an Encrypted Mode SYNC or SYNC/ACK control frame:
For each RLP frame transmitted, the RLP Layer shall set the value of
V(S) to the least significant 8 bits of EXT_V(S). EXT_V(S) shall be
incremented, following the procedures for incrementing V(S) that are
contained in 3.1.2.1 except that EXT_V(S) shall be incremented modulo
230 .
The RLP Layer shall maintain a 30-bit extended sequence number
EXT_V(R). When the RLP Layer is initialized or reset, the RLP Layer
shall set the least significant 8 bits of EXT_V(R) to zero. The most
significant 22 bits of EXT_V(R) shall be set as described in
3.1.1.2.2.1 or 3.1.1.2.2.2 as appropriate.
When V(R) changes (see 3.1.2.1), the RLP Layer shall change
EXT_V(R) by the same amount.1
When authentication is performed during the establishment of a CDMA
Traffic Channel, the mobile station and BS/MSC shall set the input
parameters of the DataKey_Generation procedure defined in ``Common
Cryptographic Algorithms, Revision A. 1'' as follows:
The mobile station and BS/MSC shall then perform the DataKey_Generation
procedure. The data encryption key (DataKey) and L table shall not
change while the Traffic Channel is established.
Mobile stations and BS/MSCs supporting RLP data encryption shall perform
negotiation of RLP data encryption using the procedures in 3.1.1.2.2.1
or 3.1.1.2.2.2, respectively.
When the RLP Layer sends an Encrypted Mode SYNC or SYNC/ACK RLP control
frame with the EM field set to '01', the RLP Layer shall set the
EXT_SEQ_M field to the most significant 22 bits of the current value
of EXT_V(S).
If the EM field is not included in a received RLP control frame, the
receiving RLP Layer shall process the message as if EM were included and
set to '00'. Throughout the following procedures, the transmitting RLP
Layer may send Non-Encrypted Mode RLP control frames whenever the EM
field would be set to '00'.
If the BS/MSC requests RLP data encryption, the BS/MSC may deny access
to service if authentication procedures (see 6.3.12 of TIA/EIA/IS-95-A)
are not performed during Traffic Channel establishment, or if the mobile
station indicates by the setting of the EM field that it does not
perform RLP data encryption.
If the mobile station can perform RLP data encryption, the mobile
station shall send an Encrypted Mode SYNC RLP control frame to initiate
Encrypted Mode Initialization/Reset. The mobile station's RLP Layer
shall set the EM field to '01' and shall set the EXT_SEQ_M field to
the most significant bits of the mobile station's current value of
EXT_V(S).
If the mobile station cannot perform RLP data encryption, the mobile
station's RLP Layer shall set the EM field to '00' (or equivalently,
send a Non-Encrypted Mode SYNC RLP control frame to initiate
Non-Encrypted Mode initialization/reset).
When the mobile station RLP Layer receives an Encrypted Mode SYNC RLP
control frame, it shall perform the following:
When the mobile station RLP Layer receives an Encrypted Mode SYNC/ACK
RLP control frame, it shall perform the following:
When the mobile station RLP Layer receives an Encrypted Mode ACK RLP
control frame, it shall perform the following:
When the BS/MSC RLP Layer transmits an Encrypted Mode SYNC RLP control
frame, it shall perform the following:
When the BS/MSC RLP Layer receives an Encrypted Mode SYNC/ACK RLP
control frame, it shall perform the following:
When the BS/MSC RLP Layer receives an Encrypted Mode ACK RLP control
frame, it shall perform the following:
When transferring data, non-transparent RLP is a pure NAK-based
protocol. That is, the receiver does not acknowledge correct RLP data
frames; it only requests the retransmission of RLP data frames that were
not received.
All operations on RLP frame sequence numbers shall be carried out in
unsigned modulo 256 arithmetic. Comparisons of two RLP frame sequence
numbers shall also be modulo 256: for any RLP frame sequence number N,
those sequence numbers from (N+1) modulo 256 to (N+127) modulo 256,
inclusive, shall be considered greater than N while all sequence numbers
from (N-128) modulo 256 to (N-1) modulo 256, inclusive, shall be
considered less than N.3
The RLP layer shall maintain an 8-bit sequence number count V(S) for all
transmitted RLP data frames (see Figure 3.1.2.1-1). The sequence number
field (SEQ) in each new RLP data frame sent and in each RLP idle frame
sent shall be set to V(S). V(S) shall be incremented, modulo 256, after
formatting each new RLP data frame sent that contains a non-zero number
of data octets. V(S) shall not be incremented after an RLP idle frame is
sent. New RLP data frames shall not be segmented.
3.1.1.1 Non-Encrypted Mode Initialization and Reset
3.1.1.2 Encrypted Mode RLP Initialization/Reset
3.1.1.2.1 Extended Data Frame Sequence Numbering
Mobile stations and BS/MSCs supporting RLP data encryption shall support
the following extended data frame sequence numbering for RLP data
frames.
3.1.1.2.2 RLP Data Encryption Negotiation
3.1.1.2.2.1 Mobile Station Negotiation Procedures
3.1.1.2.2.2 BS/MSC Negotiation Procedures
When the BS/MSC RLP Layer receives an Encrypted Mode SYNC RLP control
frame, it shall perform the following:
3.1.2 Data Transfer
3.1.2.1 Non-Encrypted Data Transfer
|
|
The RLP layer shall provide a storage buffer for resequencing of out-of-sequence RLP data frames both on the transmitting and on the receiving side.4 These buffers shall each be able to store no fewer than 128 RLP data frames of the maximum size allowed for the traffic type carrying RLP.
For each received RLP data frame that is valid and contains a non-zero number of data octets, the RLP layer shall compare the sequence number to V(R) and V(N). Criteria for frame validity are given in 3.1.3.
On receiving a NAK, the RLP layer shall insert copies of the requested
RLP data frame(s) into its output stream. If the NAK
includes any
sequence number greater than or equal to V(S)5, the RLP layer shall perform the
initialization/reset procedures specified in 3.1.1.1 or 3.1.1.2.
If the size of a retransmitted frame is less than or equal to the number
of octets available in the traffic channel frame at the time of
retransmission, an unsegmented frame (see 4.3.2.1 and
4.3.2.3.2) shall be used. If the size of a retransmitted frame
exceeds the number of octets available in the traffic channel frame at
the time of retransmission, the RLP layer may segment the frame as
specified in 3.1.4.
The RLP layer shall maintain a NAK retransmission timer for each RLP
data frame requested in a NAK RLP control frame.
The NAK retransmission timer shall be implemented as a frame
counter. The NAK retransmission counter shall be incremented for each
valid RLP idle frame and for each valid new RLP data frame (sequence
number greater than or equal to V(R)) received on the traffic type where
the RLP is carried. When RLP frames are carried as primary traffic, the
RLP receiver shall not increment the NAK retransmission counter upon
receiving a Blank RLP frame.
When RLP is used with Multiplex Option 1 and is carried as secondary
traffic, frame types 2, 3, 4, and 5 (see 6.2.2.2.2 of TIA/EIA/IS-95) are
not considered RLP frames and are not counted.
When RLP is used with Multiplex Option 2 and is carried as secondary
traffic, frame types 3, 4 and 5 (see 6.2.2.2.1 of TIA/EIA/IS-95) are not
considered RLP frames and are not counted.
The NAK retransmission counter shall not be incremented on receiving
erasures (as defined in 3.1.3), RLP control frames,
Intersegment Fill frames nor old RLP data frames (sequence number less
than V(R)). The NAK retransmission counter shall be
considered expired when it is incremented to an implementation dependent
value greater than RLP_DELAY6.
If any RLP data frame requested has not arrived when its NAK
retransmission timer expires, the receiver shall send one or more NAK
RLP control frames requesting the retransmission of all unreceived RLP
data frames from V(N) upward. RLP data frames requested in a previous
NAK RLP control frame whose NAK retransmission timer or NAK abort timer
has not expired should not be included in these NAK frames. Each NAK RLP
control frame transmitted as the result of a NAK retransmission timer
expiration shall be transmitted twice. The RLP layer shall then restart
the NAK retransmission timer for the RLP data frames requested.
If any RLP data frame requested has not arrived when its NAK
retransmission timer expires for the second time, the receiver shall
send one or more NAK RLP control frames requesting the retransmission of
all unreceived RLP data frames from V(N) upward. RLP data frames
requested in a previous NAK RLP control frame whose NAK retransmission
timer or NAK abort timer has not expired should not be included in these
NAK frames. Each NAK RLP control frame transmitted as the result of a
second NAK retransmission timer expiration shall be transmitted three
times. The RLP layer shall then start a NAK abort timer for the RLP data
frames requested. The NAK abort timer shall be implemented, and shall be
considered expired, according to the same rules as a NAK retransmission
timer.
If any RLP data frame requested has not arrived when its NAK abort timer
expires, the RLP layer shall set V(N) to the sequence number of the next
missing frame, or to V(R) if there are no remaining missing frames. The
RLP layer shall then pass any RLP data frames with sequence numbers less
than V(N) in order of sequence number to the higher layer. Further
recovery is the responsibility of the upper layer protocols.
The RLP layer shall perform the following whenever RLP frames are
carried as secondary traffic:
When RLP data encryption is negotiated, the Data octets of all
transmitted RLP data frames shall be encrypted, using the following
procedures.
Encryption mask generation shall be in accordance with the Data_Mask
procedure defined in ``Common Cryptographic Algorithms, Revision A. 1.''
When an RLP data frame is transmitted, the RLP layer shall set the input
parameters of the Data_Mask procedure, HOOK and LEN (see ``Interface
Specification for Common Cryptographic Algorithms, Revision A. 1'') as
follows:
The RLP layer shall then execute the Data_Mask procedure. Each octet
of the Data part of the RLP data frame shall be combined with the mask
by bitwise exclusive-or, combining successive data octets with mask
octets.
RLP data frames that are retransmitted shall be encrypted using the same
mask as when first transmitted.
If an RLP data frame for retransmission is to be sent as segmented RLP
data, the data frame shall be encrypted prior to its segmentation.
For each RLP data frame received, the RLP layer shall form an extended
sequence number EXT_SEQ which shall be set equal to EXT_V(R) (see
3.1.1.2.1) minus the difference between V(R) (see
3.1.2.1) and the received sequence number.8 For this calculation, if the
received sequence number changes V(R) and EXT_V(R), the new values of
V(R) and EXT_V(R) shall be used in the calculation of
EXT_SEQ.9
When an encrypted RLP data frame is received, the RLP layer shall set
the input parameters of the Data_Mask procedure (see ``Interface
Specification for Common Cryptographic Algorithms, Revision A. 1'') as
follows:
The RLP layer shall then execute the Data_Mask procedure. Each octet
of the Data part of the RLP data frame shall be combined with the mask
by bitwise exclusive-or, combining successive data octets with mask
octets.
If a retransmitted RLP data frame is received as 2 or more segmented RLP
frames, the unsegmented frame shall be reassembled prior to decrypting
the data.
When RLP frames are carried as primary traffic, the RLP layer shall
discard as invalid all traffic channel frames received for which any of
the following applies:
All other traffic channel frames shall be considered valid.
If three consecutive identical Rate 1/8 frames arrive with a sequence
number that is out of the acceptable range, as defined in (6) above,
then:
The RLP layer shall maintain a count E of the consecutive frames
classified as ``erasures,'' as defined in (1) above. If the consecutive
erasure count E exceeds 127, the RLP layer shall perform the
initialization/reset procedure specified in 3.1.1.
All other traffic channel frames shall be considered valid, and shall be
processed by RLP if they contain secondary traffic data.
The RLP layer shall maintain a count E of the consecutive frames
classified as ``erasures,'' as defined in (1) above.
If the consecutive erasure count E exceeds 127, the RLP layer shall
perform the initialization/reset procedure specified in 3.1.1.
The following procedures apply to the segmentation and reassembly of RLP
data frames. Segmentation may be necessary when a retransmitted frame
size exceeds the number of octets available at the time the
retransmission occurs.
The RLP layer procedures below assure that no more than three data
bearing segments are needed to transmit an RLP frame by requiring all
but the last segment to use at least a Rate 3/8 frame.11
A retransmitted RLP data frame may be sent in one, two or three
segments. If the retransmitted frame is sent in a single segment, an
unsegmented frame (see 4.3.2.1 and 4.3.2.3.2) is
used. If the retransmitted RLP data frame size exceeds the number of
octets available at the time the retransmission occurs, the RLP layer
should segment the frame. With the exception of intersegment fill
frames, all RLP segmented frames except the last segmented frame shall
be sent using Rate 3/8 or larger RLP frames.
When Rate Set 2 is used, an Intersegment Fill frame (see
4.3.2.2 and 4.3.2.2.1) can be sent by the
BS/MSC. Mobile stations complying with this standard shall not transmit
intersegment fill frames on the reverse link. When the intersegment fill
frame is used the sequence number of an Intersegment Fill frame shall be
set equal to the sequence number of the RLP data frame being
retransmitted.
The RLP layer segments the frame using the following procedure:
The RLP layer shall begin frame reassembly on receipt of the first
segment of a segmented RLP data frame. When RLP is carried with
Multiplex Option 2, if an Intersegment Fill frame is received, the RLP
layer shall discard it. When the last segment of the RLP data frame is
received, the RLP layer shall process the RLP data frame in the same
manner as if it had been unsegmented (see 4.3.2.1).
The RLP layer shall discard, without further processing, any segmented
RLP data frame that is received under any of the following conditions:
Transparent RLP maintains two state variables, V(S), and V(R) (see
3.2.2). When a service option using transparent RLP is
connected, the transparent RLP layer shall perform the following:
Transparent RLP does not provide any retransmission of erased frames. It
is the responsibility of the upper layers to provide further
synchronization and error recovery when Transparent RLP is used.
Transparent RLP shall maintain two eight-bit sequence number variables,
V(S) (for transmitting) and V(R) (for receiving). See 3.2.1 for
initialization procedures for these state variables.
If Transparent RLP has no data to send, Transparent RLP generates and
transmits an idle RLP frame (see 4.3.3). When an idle RLP frame
is sent, transparent RLP shall set the SEQ field to the current value of
V(S). V(S) shall not be incremented when Transparent RLP sends an idle
RLP frame. When an idle RLP frame is received by Transparent RLP,
Transparent RLP may discard it.
When a transparent RLP frame is to be transmitted the RLP transmitter
shall perform the following:
When a transparent RLP data frame is received the transparent RLP
receiver shall perform the following:
Transparent RLP sublayer shall discard as invalid all traffic channel
frames received which are classified into category 26 by Multiplex
Option 2 (see 6.2.2.2 of TIA/EIA/IS-95).
The following requirements for traffic channel rate control shall apply
to mobile stations having a single connected service option. Traffic
channel rate control for mobile stations having multiple connected
service options is for further study.
If the mobile station receives a Service Option Control Order
having an ORDQ field in which the 3 MSBs have values given in Table
3.3.1-1, then the mobile station shall generate the fraction P of those
new traffic channel frames normally generated as full-rate frames at
either full rate (Rate 1) or half rate (Rate 1/2) as specified by the
corresponding line in the table. While the traffic channel is active the
mobile station shall continue to use these fractions until the mobile
station receives a Service Option Control Order that specifies
different fractions.
Whenever a traffic channel first becomes active, the mobile station
shall set the fraction P to 1.
3.1.2.2 Encrypted Data Transfer
3.1.2.2.1 Encryption
3.1.2.2.2 Decryption
3.1.3 Frame Validity Checks
3.1.3.1 Primary Traffic
3.1.3.2 Secondary Traffic
When RLP frames are carried as secondary traffic, the RLP layer shall
discard as invalid all traffic channel frames received for which any of
the following applies:
3.1.4 Segmentation of Retransmitted Data Frames
3.2 Transparent RLP Procedures
3.2.1 Initialization
3.2.2 Data Transfer
When the transparent RLP receives an idle frame from the multiplex
sublayer, the transparent RLP receiver shall discard the frame.
3.2.3 Frame Validity Checks
Transparent RLP shall discard as invalid all traffic channel frames
received which are classified into category 9 or 10 by Multiplex Option
1 (see 6.2.2.2 of TIA/EIA/IS-95).
3.3 Traffic Channel Rate Control
3.3.1 Service Option Negotiation Rate Control Procedures
The BS/MSC may send a Service Option Control Order to the mobile
station on the Forward Traffic Channel (see 7.7.4 of
TIA/EIA/IS-95-A). The mobile station shall not send Service Option
Control Orders for the purpose of rate control to the BS/MSC.
|
The mobile station may use the following procedure to perform this rate reduction. Sequences of N frames are formed as shown in Table 3.3.1-2. The first L traffic channel frames in this sequence are allowed to be at Rate 1, the next N-L frames are forced to be Rate 1/2. Whenever the RLP layer has no more octets to send than fit in a Rate 1/2 RLP data frame, a Rate 1/2 RLP data frame shall be sent, and the sequence shall be reset. This ensures that the first traffic channel frame in a burst of data will be at Rate 1, unless ORDQ equals '100XXXXX' or the RLP layer has been commanded by the multiplex sublayer to generate other than a Rate 1 frame.
|
|
|
The BS/MSC shall set this field to the RATE_REDUC value from Table 3.3.2.2-2 corresponding to the rate reduction that the mobile station is to perform.
The BS/MSC shall set this field to '00'.
The BS/MSC shall set this field to '000'.
|
Non-transparent RLP shall send and receive traffic channel frames in accordance with the requirements of IS-95 Multiplex Options 1 and 2.
Non-transparent RLP frames can be transmitted as primary traffic or as secondary traffic. Service options may support any subset of the available traffic types and RLP frame types to carry non-transparent RLP.
Mobile stations supporting multiple connected service options may support independent instances of non-transparent RLP for each service option, but each traffic type shall carry only a single instance of non-transparent RLP. RLP data frames sent on one traffic type shall not be retransmitted on another traffic type.
Non-transparent RLP frames shall not be sent on the Access and Paging Channels. The frame formats defined in 4.3.1 through 4.3.3 can be carried by the following Multiplex Option 1 frames (see 6.1.3.3.11 and 7.1.3.5.11 of TSB74).
The frame formats defined in 4.3.1 through 4.3.3 can be carried by the following Multiplex Option 2 frame formats (see 6.1.3.3.12 and 7.1.3.5.12 of TSB74):
For full rate primary traffic only, two special frame formats are defined in 4.3.2.3. The information field of the first format corresponds to an RLP control or data frame as defined in 4.3.1 and 4.3.2 respectively. The second frame format contains a sequence number and user data only and allows maximum throughput.
Transparent RLP frames can be transmitted as primary traffic only. Service options may support any subset of the RLP data frame types to carry transparent RLP.
Mobile stations supporting multiple connected service options may support a single instance of Transparent RLP. Transparent RLP frames shall not be sent on the Access and Paging Channels.
The frame formats defined in 4.3.2 below can be carried by the following Multiplex Option 1 frames (see 6.1.3.3.11 and 7.1.3.5.11 of TSB74):
The frame formats defined in 4.3.2 below can be carried by the following Multiplex Option 2 frames (see 6.1.3.3.12 and 7.1.3.5.12 of TSB74):
For full rate primary traffic only, transparent RLP may use the Full Rate Format B frame, as defined in 4.3.2.3.2.
RLP control frames are distinguished by the CTL field. RLP control frames are not themselves sequence numbered, but contain the next data sequence number, in order that erased RLP data frames may be quickly detected. The sequence number is not incremented after an RLP control frame.
Certain RLP control frames (specifically the NAK message) may refer to the sequence numbers of other RLP data frames.
|
When the EM field is set to '01', this field shall carry the most significant bits of the extended data frame sequence number. Otherwise, this field shall be set to all zeros.
When included, contents of this field shall be set to the 22 most significant bits of EXT_V(S) (see 3.1.1.2.2).
|
|
Table 4.3.2.1-1. Values of the Maximum Allowable Data Length (MAX_LEN) 10
4.3.2.2 Segmented RLP Data Frames
Segmented RLP data frames carry a variable number of data octets, using a length field to
indicate the number of octets. This type of data frame shall be used only to carry
retransmitted RLP data frames (see 3.1.4).
|
|
For RLP frames carried on full rate primary traffic frames, two special
frame formats described in 4.3.2.3.1 and 4.3.2.3.2
shall be used. For RLP frames carried on half-rate or quarter rate
frames, RLP data frames or RLP control frames, as defined in
4.3.2 and 4.3.2.1, apply directly.
For Multiplex Option 1, full rate format A frames are defined as
follows:
4.3.2.3 Primary Traffic
4.3.2.3.1 Full Rate Format A
IS-95 full rate primary traffic frames of format A can carry either RLP data frames or RLP
control frames, as defined in 4.3.1 and 4.3.2.
|
For Multiplex Option 2, full rate format A frames are defined as follows:
|
4.3.2.3.2 Full Rate Format B
For Multiplex Option 1, format B carries 20 octets of data, as follows:
|
For Multiplex Option 2, format B carries 32 octets of data, as follows:
|
For Multiplex Option 1, Rate 1/8 RLP frames are RLP idle frames. For Multiplex Option 2, Rate 1/8 primary traffic RLP frames and Rate 1/16 secondary traffic RLP frames may be RLP idle frames. Higher rate RLP data frames with zero length (LEN = 0) (see 4.3.2.1) are also RLP idle frames, and may be sent as an alternative.
|
Let the sequence number to be coded be denoted as
|
Let the FCS be denoted as
|
The FCS is generated as follows:
|
Where Å denotes modulo-2 addition. Code bits Y1 through Y6 are found by cyclically shifting X0 through X6 . In other words, X(i+j)mod 7 is substituted for Xi in the generating equation for Yj. Y7 is a parity bit over the previous 15 bits. The final step in generating the FCS is to complement the last three bits. A table specifying the code is provided in Table 4.3.3-1.
Table 4.3.3-1 presents the modified Nordstrom-Robinson code used to protect Rate 1/8 and Rate 1/16 RLP idle frames. In Table 4.3.3-1, the most significant byte in a word is the SEQ value to be protected and the least significant byte is the FCS. All numbers are hexadecimal.
Table 4.3.3-1. Modified Nordstrom-Robinson Code 2
|
1That is, if the old value of V(R) is A and the new value of V(R) is B, EXT_V(R) is incremented by (256+ B-A) modulo 256. All arithmetic operations on EXT_V(R) are modulo 230.
2It is anticipated that future revisions of PPP, IP and other protocols may include encryption.
3Note that (N-1) modulo 256 is equal to (N+255) modulo 256, and (N-128) modulo 256 is equal to (N+128) modulo 256.
4ie. two such buffers are required in a mobile station.
5This would indicate that the NAK process has fallen behind the sequence numbering by more than 128 frames.
6It is recommended that a guard interval of five frames be added to the retransmission timeout to account for buffering within the TIA/EIA/IS-95-A mobile or base station and for segmentation of retransmitted frames.
7When RLP is carried as secondary traffic, an RLP idle frame is an RLP data frame with zero length (see 4.3.2.1).
8That is, if the received sequence number is N, EXT_SEQs is set to EXT_V(R)-((256+ V(R)-N) modulo 256).
9This ensures that the received sequence number is never less than V(R).
10The ``erasures'' defined here serve to inhibit incrementing of the NAK retransmission timer. They are not to be confused with TIA/EIA/IS-95 frame erasures.
11For Multiplex Option 1, the smallest available frame that carries data is Rate 1/2, which is larger than Rate 3/8.
12RLP would be carried as both primary and secondary traffic simultaneously if there are two service options active (one using primary traffic and the other using secondary traffic), each with its own instance of RLP.
13RLP would be carried as both primary and secondary traffic simultaneously if there are two service options active (one using primary traffic and the other using secondary traffic), each with its own instance of RLP.
14With the exception of the last segmented frame, Rate 1/4 RLP frames may not carry segmented RLP data frames(see 3.1.4).
15Note that the most significant bit of the CTL field of a control frame and a segmented data frame is always set to '1'.
