Backwards-Compatible Protocol Header Extension for LTE
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Solution Overview
Problem
The existing LTE protocol stacks, particularly the MAC, RLC, and PDCP layers, face limitations in supporting high data rates due to constraints in length and sequence number fields, leading to inefficient data transmission and underutilization of available radio resources.
Innovation Solution
The introduction of an extended header structure that logically concatenates legacy indicator fields with additional indicator fields, allowing for increased bit lengths and sequence numbers without altering the bit-wise contiguous nature of existing fields, thereby supporting higher data rates while maintaining backwards compatibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the existing LTE protocol formats (Rel-8/9) are used, then backwards compatibility is maintained, but the maximum Transport Block size is limited to 32767 octets and cannot support high data rates up to 3 Gbps
Solution Approach 1:
The patent embeds an extended header structure within the existing MAC PDU framework. The extended header containing the extended L field is nested inside the MAC PDU, allowing legacy devices to ignore the extension while enhanced devices can utilize the extended capacity. This nesting enables the system to support both legacy and enhanced formats within the same protocol structure.
Solution Approach 2:
The patent introduces dynamic field expansion where the L field can be extended from 15 bits to 23 bits based on the transport block size requirements. The extension is dynamically activated when the transport block size exceeds 32767 octets, allowing the protocol to adapt its capacity to match the actual data transmission needs while maintaining backward compatibility.
2Productivity
If the L field is extended to support larger Transport Block sizes, then high data rates are enabled, but the header structure complexity increases
Solution Approach 1:
The L field is segmented into a legacy L field (15 bits) and an extended L field (8 bits). The extended L field is further divided into an extension indicator (1 bit) and extended length bits (7 bits). This segmentation allows the protocol to maintain the original 15-bit L field for legacy compatibility while adding optional extension capabilities through clearly defined sub-fields.
Solution Approach 2:
The extension indicator field acts as an intermediary that signals whether the extended L field is present in the header. This intermediary element allows receiving devices to determine whether to parse the extended length bits, simplifying the processing logic by providing a clear conditional marker rather than requiring devices to always handle the full extended structure.
3Adaptability or versatility
If multiple MAC SDUs are used per transport block, then data transmission flexibility is improved, but the number of required sequence numbers increases, exhausting the 10-bit RLC SN space
Solution Approach 1:
The patent enables a single MAC SDU to serve multiple logical channels through the extended L field capability. By allowing one MAC SDU to carry data for multiple logical channels when the extended header is used, the system reduces the need for multiple separate MAC SDUs and their associated sequence numbers, thereby conserving the limited 10-bit RLC SN space while maintaining transmission flexibility.
Data Source
AI summary
Fields such as sequence numbers and length indicators of protocol layers are extended in extended headers so as to be backwards compatible with corresponding legacy headers. The existing fields of the legacy headers are not directly extended. Instead, existing fields are logically concatenated with other fields of the extended header. Whether the extended fields or legacy fields will be used can be determined dynamically based on current transport block size or semi-statically by higher layers.