Layer 2 protocols consists fo 4 protocol entities:
1. MAC (Medium access control)
2. RLC (Radio link control)
3. PDCP (Packet data convergence protocol)
4. BMC (Broadcast and multicast control)
Consider TTI = 20ms
peak data rate = 64 kbps
trasnport block size = 336 bits
RLC SDU size = 500 bytes
SN=6, 8 are dropped.
SN = Sequence Number
P = Poll bit
The physical layer combines the transport blocks together, interleaves them and then transmits them via two radio frames.
Thus, RLC PDUs in the receiver cannot be recovered until all [...]
There are two types of PDUs in RLC/AM:
1. AM data (AMD) PDUs: user data
2. AM control PDUs
AM control PDUs are further classified into:
1. STATUS PDU
2. Piggybacked STATUS PDU
3. RESET and RESET ACK PDU
RLC provides 3 different mode:
1. transparent
2. unacknowledged
3. acknowledged mode
Each mode provides a different set of services to the higher layers.
Some of them are
1. segmentation and reassembly
2. concatenation
3. reliable transfering data
4. flow control
5. in-sequence delivery
6. Error correction by ARQ(automatic repeat request)
In general, RLC instance exists per service.
(there are some few exceptions such as speech and signaling where multiple RLC entities per service.)
The configuration or the RLC depend on the specific QoS for the service.
Layer 2 comprises of 4 protocol entities.
1. MAC protocol
2. RLC protocol
3. PDCP (packet data convergence protocol)
4. BMC (broadcast and multicast control) protocol
No!
MAC layer transfer service is done in unacknowledged mode. That is, no guaranteed delivery service.
RLC layer has mechanisms to detect errors and retransmit.
Radio interface protocol structure:
Note that RB vs. SRB
At the UTRAN side, RLC and above protocols are located at RNC.
MAC protocols: some functionalities are at Node B, others are at RNC.
