HSDPA MAC-hs Packet Segmentation for VoIP Delay Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional HSDPA systems face challenges in effectively transferring real-time traffic, especially for users under poor channel conditions, due to inadequate handling of packet sizes and retransmissions, which results in undesirable delays for delay-sensitive applications like VoIP.
Innovation Solution
The method involves segmenting larger packets into smaller ones at the MAC-hs layer to allow for more reliable transmission of smaller segments over multiple TTIs, using lower modulations and higher coding rates, and coordinating segmentation and reassembly between the Node-B and WTRU through a new MAC-hs header or HS-SCCH, reducing the need for H-ARQ retransmissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If larger transport blocks are transmitted to improve data rate, then throughput increases, but error probability increases under poor channel conditions
Solution Approach 1:
The patent segments a large transport block into multiple smaller sub-blocks that can be transmitted separately. Each sub-block is encoded and transmitted independently, allowing the receiver to successfully decode data even if some sub-blocks experience errors. This resolves the contradiction by enabling higher effective throughput through successful sub-block reception while maintaining reliability through error isolation in poor channel conditions.
2Productivity
If higher coding rates are used to increase data rate, then spectral efficiency improves, but transmission reliability deteriorates
Solution Approach 1:
The transport block is divided into multiple sub-blocks that can be transmitted with different coding rates adapted to channel conditions. This allows the system to use higher coding rates for sub-blocks in good channel conditions (improving spectral efficiency) while using lower coding rates for sub-blocks in poor conditions (maintaining reliability), thus resolving the contradiction between spectral efficiency and transmission reliability.
3Reliability
If conventional H-ARQ retransmissions are used to ensure reliable delivery, then packet delivery reliability improves, but delay increases for real-time traffic
Solution Approach 1:
The patent performs preliminary segmentation and encoding of the transport block into multiple sub-blocks before transmission. By pre-processing the data into independently decodable units, the system enables the receiver to successfully reconstruct the original data from received sub-blocks without requiring retransmissions. This preliminary action resolves the contradiction by ensuring reliable delivery through advance preparation, thereby avoiding time loss from retransmissions.
4Device complexity
If fixed transport block sizes are used to simplify scheduling, then system complexity reduces, but adaptability to varying channel conditions deteriorates
Solution Approach 1:
The patent segments transport blocks into sub-blocks with sizes that can be dynamically adjusted based on channel conditions. The segmentation allows the system to adapt the number and size of sub-blocks to match current channel quality, providing flexibility without requiring complete redesign of the scheduling framework. This resolves the contradiction by enabling channel condition adaptability through segmented structures while maintaining relatively simple scheduling mechanisms.
Data Source
AI summary
A method and apparatus for transmitting and receiving a packet via high speed downlink packet access (HSDPA) are disclosed. At least one HSDPA medium access control (MAC-hs) service data unit (SDU) is segmented into a plurality of segments. MAC-hs protocol data units (PDUs) are generated from the segments wherein each MAC-hs PDU includes at least one segment. Each MAC-hs PDU may include one segment from a single MAC-hs SDU. The size of the segments may match to the size of the MAC-hs PDUs minus the size of the header of the MAC-hs PDU. The sizes of the segments may be determined based on the number of segments to which the MAC-hs SDU is segmented. Alternatively, each MAC-hs PDU may include a combination of segments from a plurality of MAC-hs SDUs or a combination of at least one segment from one MAC-hs SDU and at least one entire MAC-hs SDU.