Engineering & Industrial Services

Forward-Looking SoC-based PHY Architecture for Macro and Small Cell LTE eNode-Bs

This white paper describes an efficient, forward-looking architecture that enables the handling of various form factors of Long Term Evolution (LTE) base stations with minimal software modification, and without architecture changes

Current Trends in Base Station SoCs
LTE and LTE-A base station (eNode-B) baseband design challenges such as higher data rates and lower latency have compelled designers to adopt design methodologies that predominantly leverage heterogeneous system designing. Putting together ASICs and heterogenous processors have resulted in SoC solutions which perform the functions of several independent processors and boards at a small fraction of the earlier cost and power consumption Typical SoCs for wireless base stations today consist of DSP cores, HL cores, Standard accelerator ASICs, RF interfaces, inter-board intefaces and peripherals.

Evolution of SoCs for 4G systems
SoCs have been evolving in terms of accelerating different blocks in the Physical Downlink Shared CHannel (PDSCH) and the Physical Uplink Shared Channel (PUSCH) chains in an eNodeB. In reality, several vendors offer SoCs for 3G and 4G systems, each with unique features and advantages. Thus, the generic analysis of LTE will not precisely fit any available SoC.

For LTE-A and for macro cells with multiple sectors or carriers, many sets of cores and hardware accelerators will be needed. It is a challenge to design a software architecture that can easily migrate to more powerful SoCs and scale up to the available processing power.

Forward looking and Flexible architecture
Considering the evolution of SoCs, a systematic approach for software architecture and design can cater to all generations of SoCs. An architecture that adheres to the following principles is likely to be more 'forward-compatible:

  • Principle 1. Software design should cater to a family of SoCs, rather than a single SoC.
  • Principle 2. Hardware accelerators of next-generation SoCs should be mimicked in unique DSP cores in the current generation SoCs
  • Principle 3. Inherent virtual addressing to isolate sector contexts (in a multi-sector deployment) should be exploited.
  • Principle 4. Flexibility in the framework for deploying software modules in different cores

LTE/LTE-A eNode-B design is challenged by the need for handling various base station requirements which require software architecture changes and the corresponding code changes. A forward looking architecture will address these challenges, at least partly, on the existing hardware itself.

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