Wireless communication standards such as Long Term Evolution (LTE) are rapidly changing to support the high data rate of wireless devices. The physical layer baseband processing has strict real-time deadlines, especially in the next-generation applications enabled by the 5G standard. Existing base station transceivers utilize customized Digital Signal Processing (DSP) cores or fixed-function hardware accelerators for physical layer baseband processing. However, these approaches incur significant non-recurring engineering costs and are inflexible to newer standards or updates. Software programmable processors offer more adaptability. However, it is challenging to sustain guaranteed worst-case latency and throughput at reasonably low-power on shared-memory many-core architectures featuring inherently unpredictable design choices, such as caches and network-on-chip.

We propose SPECTRUM, a predictable software defined many-core architecture that exploits the massive parallelism of the LTE baseband processing. The focus is on designing a scalable lightweight hardware that can be programmed and defined by sophisticated software mechanisms. SPECTRUM employs hundreds of lightweight in-order cores augmented with custom instructions that provide predictable timing, a purely software-scheduled on-chip network that orchestrates the communication to avoid any contention and per-core software controlled scratchpad memory with deterministic access latency. Compared to a many-core architecture like Skylake-SP (average power 215W) that drops 14% packets at high traffic load, 256-core SPECTRUM by definition has zero packet drop rate at significantly lower average power of 24W. SPECTRUM consumes 2.11x lower power than C66x DSP cores+accelerator platform in baseband processing. SPECTRUM is also well-positioned to support future 5G workloads.