Reliability and longer range for low power transmitters with on demand network MIMO

Abstract

We propose a new approach for the uplink in a one-hop multi-gateway wireless packet network. In principle, the proposed technique applies to many types of low-power transmitters, including wireless sensors and RFID tags, both active and passive. Only when requested, each gateway node (or listener) forwards the compressed physical layer samples of packets to a server, which decodes the packets using multiple-input-multipleoutput (MIMO) techniques; this functionality could be described as selective application of multi-user MIMO with a distributed receiver array. Packets that have adequate SINR at a gateway are decoded, i.e., captured, and their waveforms are reconstructed and subtracted from stored samples; this subtraction is interference cancellation (IC). After IC, weaker packets may be revealed and decoded by the gateway, enabling successive IC (SIC). The diversity gain of multi-gateway reception provides higher SNR to packets that are not decodable at any gateway, thereby extending range. The spatial multiplexing capability of MIMO enables packets that have too much interference at the gateways to be decoded at the server, thereby supporting energy saving transmit-only strategies. The selectivity or "on demand" feature lowers the fronthaul cost of sending samples to the server. This paper presents preliminary simulation and experimental performance results and overviews the various design concerns of On Demand Network MIMO, such as synchronization, spreading, SIC performance, gateway deployment, and medium access control (MAC).

Optimized Gateway Placement for Interference Cancellation in Transmit-Only LPWA Networks

“…For example, a bandwidth efficient high-order quadratic amplitude modulation (QAM) with no error correction code can necessitate a high value for , whereas a power efficient high-order frequency shift keying modulation coupled with an error correction code can enable a low value for [ 31 ]. On the other hand, z is mainly controlled by the quality of the cancellation, which in turn, depends on the quality of synchronization and channel estimation, which is usually performed based on the packet ’s preamble and training sequence or pilot symbols [ 32 , 33 ]. For example, a long preamble and a long training sequence (and a low-Doppler channel, i.e., long coherence time) can enable a low value of z , whereas short versions of these will cause poor cancellation and a high value of z .…”

Adaptive Channel Assignment With Predictions of Sensor Results and Channel Occupancy Ratio in PhyC-SN

“…However, when the load from the simultaneous wireless access of sensors exceeds the spreading gain, the packet error rate rapidly degrades, which can drastically degrade communication quality. Methods involving multi-user, multi-input, multi-output [8] and non-orthogonal multiple access [9] technologies also enable the simultaneous wireless access of multi-antenna systems. However, such methods cause increases in delay times owing to the complicated processing required for separation of a signal.…”