Short ACK/NACK Bitmap Encoding in EDGE RLC/MAC Blocks
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Solution Overview
Problem
Existing ARQ signaling methods in EDGE compliant systems waste resources due to frequent ACK/NACK messages, especially in few timeslots, leading to inefficient data transmission and potential errors in decoding short bitmaps.
Innovation Solution
The method involves encoding short ACK/NACK bitmaps independently of the payload data part's redundancy code, using a more robust modulation and coding scheme, and allocating them in various parts of the RLC/MAC block, such as the header or a new broadcast/multicast zone, to enhance reliability and flexibility in both uplink and downlink transmissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If frequent ACK/NACK messages are transmitted to ensure reliable feedback, then reliability of data transmission is improved, but bandwidth consumption increases and data transmission efficiency deteriorates
Solution Approach 1:
The patent segments the feedback mechanism by separating ACK/NACK signaling from data transmission. Instead of using dedicated uplink resources for ACK/NACK messages, the feedback is embedded within downlink data blocks as short bitmaps. This segmentation allows feedback to be transmitted without consuming uplink bandwidth, resolving the contradiction between reliable feedback and transmission efficiency.
Solution Approach 2:
The patent merges the feedback function with the downlink data transmission by incorporating ACK/NACK bitmaps within the downlink RLC/MAC blocks. This combining approach allows the system to achieve reliable feedback transmission while utilizing existing downlink resources, thereby maintaining data transmission efficiency without requiring additional uplink bandwidth.
2Device complexity
If ACK/NACK bitmaps are transmitted using the same coding scheme as payload data, then device complexity is reduced, but reliability of bitmap decoding deteriorates
Solution Approach 1:
The patent applies local quality by using different coding schemes for different parts of the transmitted data. Specifically, the ACK/NACK bitmap portion is encoded with a more robust coding scheme than the payload data, while keeping the overall structure unified. This localized enhancement of coding robustness ensures reliable bitmap decoding without significantly increasing overall system complexity.
Solution Approach 2:
The patent changes the coding parameters for the bitmap portion independently from the payload. By adjusting the redundancy level and coding rate specifically for the ACK/NACK bits, the system achieves higher decoding reliability for critical feedback information while maintaining efficient coding for the bulk data transmission.
3Reliability
If dedicated uplink resources are allocated for ACK/NACK messages, then feedback reliability is improved, but available bandwidth for data transmission is reduced
Solution Approach 1:
The patent makes the downlink data blocks serve multiple functions: they simultaneously carry payload data and embedded ACK/NACK feedback for previous uplink transmissions. This multi-functionality eliminates the need for dedicated uplink feedback resources, preserving all uplink bandwidth for data transmission while ensuring reliable feedback delivery through the universal downlink channel.
Solution Approach 2:
The system uses its own downlink transmission resources to provide the feedback function that would traditionally require separate uplink resources. By making the downlink channel serve its own feedback needs, the system eliminates the need for additional dedicated feedback resources, thereby preserving maximum bandwidth for data transmission.
4Use of energy by moving object
If short ACK/NACK bitmaps are transmitted in access bursts, then battery power consumption is reduced, but transmission speed decreases
Solution Approach 1:
The patent implements periodic feedback transmission where mobile stations send ACK/NACK bitmaps at scheduled intervals within their assigned timeslots rather than continuously. This periodic action reduces power consumption by allowing the mobile station to enter low-power states between feedback opportunities, while the regular timing ensures timely feedback for delay-sensitive applications.
Data Source
AI summary
A fast ARQ mechanism operated inside 3GPP GERAN mobile radio systems uses short bitmaps, spanning only few octets, in the header of a RLC/MAC block conveying relevant ACK/NACK signalling that is transmitted either in the uplink or downlink direction, indifferently. This short bitmap which may request synchronization between transmitting and receiving frames, is encoded together with the header using coding which is more robust than that used for payload. Correct retransmission of badly received radio blocks is based on the number of RLC/MAC block periods between the instant of transmission of a radio block and the instant of reception of the short bitmap. In addition, the short bitmap is allocated in a new zone placed immediately after the header of the RLC/MAC blocks, and encoded independently of the payload using a more robust coding against the errors than the robustness of the MCS used in the payload data part.