VLSI implementation of MIMO detection using the sphere decoding algorithm

VLSI Implementation of Hard- and Soft-Output Sphere Decoding for Wide-Band MIMO Systems

“…The ML solution (3) corresponds to the path through the tree starting by the root and leading to the leaf associated with the smallest PED. The basic ideas underlying the SD algorithm, as described in [9,12], are briefly summarized as follows: The search in the tree is constrained to nodes which lie within a radius r aroundỹ (and hence, nodes from the tree are pruned for which d i s (i) is larger than r) and tree traversal is performed depth-first, visiting the children of a given node in ascending order of their PEDs. The method using this enumeration scheme is also known as the Schnorr-Euchner (SE) SD algorithm [6].…”

“…In the remainder of the chapter, the computational complexity of SD is characterized by the number of visited nodes (including the root node but excluding the leaves), which was shown in [11,12] to be closely related to the throughput of corresponding VLSI implementations.…”

“…The hard-output SD architecture described next is based on the architecture template presented in [12]. We first summarize this architecture and then describe additional techniques that substantially improve (i.e., reduce) the associated AT-product.…”

“…In the implementation [12], this forward iteration includes the sequential evaluation of (5) and the computation of the PED in (4). In the present circuit (cf.…”

“…architectures that minimize the area-delay product, we start with the VLSI implementations for hard-output SD [12] and soft-output STS-SD [11] and propose a variety of optimizations, which improve (i.e., lower) the area-delay product of the detectors. In particular, we propose a low-complexity approximation to the Schnorr-Euchner (SE) enumeration scheme and employ pipeline interleaving, which enables us to achieve the desired design goals.…”