4. Scalable Signal Detection: Dynamic Nested Clustering

In Chap. 2, we proposed a threshold-based channel sparsification approach, and showed that the channel matrices can be greatly sparsified without substantially compromising the system capacity. In this chapter and the next chapter, we endeavor to design scalable algorithms for joint signal detection in the uplink of C-RAN by exploiting the high sparsity of the channel matrix. In this chapter, we propose a dynamic nested clustering (DNC) algorithm which greatly reduces the computational complexity of MMSE detection from O(N ³) to O(N ^a), where N is the total number of RRHs and a ∈ (1, 2] is a constant determined by the computation implementations. In the next chapter, we propose a randomized Gaussian message passing (RGMP) algorithm, which further reduces the computational complexity of MMSE detection to be linear in the number of RRHs.