A unified approach to time diversity combining for fast frequency hopped NCMFSK-anti-jam processing

Abstract

Frequency hopping (FH) spread spectrum is used in communications systems to provide protection against jamming.With fast FH, there are L 2 1 hops per data symbol transmitted. In the presence of severe interference, additional protection can be obtained by processing the L M values obtained from the demodulator. This processing is termed diversity combining. Many powerful and robust types of diversity combining have been developed to reduce the effects of a large jamming signal on some of the L hops. In this paper, a survey of combining methods is presented. Simulation performance results are given for severe noise and multitone jamming (SJR = 0.0 dB). It is found that bit error rates as high as 0.4 can be reduced to < 0.1 for L < 10 using any of several diversity combining methods.

Soft Decoding Assisted Interference Cancellation in a Non-Binary LDPC Coded Fast Frequency Hopping Multiuser System Using Product Combining

“…1, resulting in M decision variables for each of the users. The decision variable recorded after PC for the kth user is given by [4] …”

“…Against this background, the novel contribution of this paper is that we extend the idea of SISO assisted SIC to product combining (PC) [4] and employ non-binary LDPC codes [5], [6] instead of binary convolutional encoding, which creates a purely symbol-based M -ary scheme. More explicitly, the M -ary symbols are encoded using LDPC codes over Galois Field (GF) (q).…”

Successive Interference Cancellation in Clipped and Product Combining aided FFH Multi-User Systems

“…PROPOSED SIC SCHEMES In this section, we propose two SIC schemes that are adapted from Fiebig' s scheme [3]. However, instead of using HLMV combining as in [3], the first SIC scheme employs the clipped combining and the second SIC scheme employs both the product combining and the clipped combining [6]. In the context of the proposed SIC schemes, the detection process consists of a conventional detection (CD) stage and multiple SIC stages.…”

“…The first proposed SIC scheme employs clipped combining [6], which is also referred to as soft limiting combining (SLC) [7]. Therefore, we refer to this scheme as the SLC-SIC scheme.…”

“…All these schemes are applicable to FFH-MFSK employing conventional hard limiting majority vote (HLMV) based combining [1], [3]. Motivated by the promising performance gains that some of the combining schemes yield compared to HLMV combining [6], [7], in this contribution, we propose two novel SIC methods, one of which invokes the clipped combining while the other employs both clipped combining and product combining. These SIC schemes are based on modifications of Fiebig's method [3], which was proposed for FFH-MFSK system employing HLMV combining.…”