Multihop Hybrid Virtual MIMO Scheme for Wireless Sensor Networks

Wireless sensor network devices commonly use a single antenna for transmission and reception, as well as for relaying packets over multiple hops to a final destination, which is referred to as single-input-single-output (SISO) multihop transmission. Advancements in multiple antenna systems enable reliable broadband wireless communications using multiple-input-multiple-output (MIMO) transmission technology. In addition, through collaboration of several single-antenna-equipped devices, cooperative MIMO communication is possible in the form of virtual MIMO (V-MIMO), virtual multiple-input-single-output (V-MISO), and virtual single-input-multiple-output (V-SIMO), which are collectively called V-MIMO technology. In this paper, a multihop hybrid V-MIMO (HV-MIMO) networking scheme is proposed to configure a minimum energy consuming route (MECR) that provides high end-to-end connectivity while satisfying end-to-end data rate and bit error rate (BER) requirements by using the best cooperative MIMO configuration for each hop. In the proposed scheme, first, the source-to-destination path is divided into long wireless communication hops, and the minimum energy consuming V-MIMO configuration is applied to each hop. Next, the long communication hops are individually evaluated for replacement with two half-length V-MIMO hops, where changes are applied only when a gain in energy consumption is obtainable. If no gain is obtainable for a certain hop, then the hop configuration is not changed, and that hop is no longer compared for replacement. This procedure of testing for possible replacement with two half-length hops is repeated individually for all hops until no further changes are made in the source-to-destination path, which is when the HV-MIMO MECR is complete. For equivalent end-to-end data rate and BER requirements, the proposed HV-MIMO multihop scheme provides a significant energy saving (e.g., 52.32% energy saving at the node density of 0.003 nodes/m2) compared with the conventional SISO multihop path's MECR. In addition, the HV-MIMO scheme always results in an energy saving gain and a significantly higher end-to-end multihop MECR connection probability compared with using the same type of cooperative MIMO configuration for each hop (i.e., homogeneous V-MIMO configuration).