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In this letter a multiuser transmitter preprocessing (MUTP) approach is proposed for downlink wireless communications, such as in spatial-division multiple-access (SDMA) or direct-sequence code-division multiple-access (DS-CDMA) system. In the proposed MUTP the preprocessing matrix is obtained by constructing a subspace that is orthogonai to the interference subspace without relying on eigen-analysis. The proposed MUTP fully removes the downlink multiuser interference, resulting in the zero-forcing (ZF) solution. It is capable of achieving the same bit error rate (BER) performance as the conventional ZF-based MUTP (ZF-MUTP). Index Terms--Pre-filtering, preprocessing, zero-forcing, multiple-input multiple-output, space-division multiple-access, direct-sequence code-division multiple-access, orthogonal subspace.

The novel family of redundant residue number system (RRNS) codes is studied. RRNS codes constitute maximum-minimum distance block codes, exhibiting identical distance properties to Reed-Solomon codes. Binary to RRNS symbol-mapping methods are proposed, in order to implement both systematic and non-systematic RRNS codes. Furthermore, the upper-bound performance of systematic RRNS codes is investigated, when maximum-likelihood (ML) soft decoding is invoked. The classic Chase algorithm achieving near-ML soft decoding is introduced for the first time for RRNS codes, in order to decrease the complexity of the ML soft decoding. Furthermore, the modified Chase algorithm is employed to accept soft inputs, as well as to provide soft outputs, assisting in the turbo decoding of RRNS codes by using the soft-input/soft-output Chase algorithm. Index Terms--Redundant residue number system (RRNS), residue number system (RNS), turbo detection.

A novel sequential estimation method is proposed for the initial synchronization of pseudonoise (PN) signals derived from m-sequences. This sequential estimation method is designed based on the principle of recursive soft-in/soft-out (SISO) decoding, and we refer to it as the recursive soft sequential estimation (RSSE) acquisition scheme. The RSSE acquisition scheme exhibits a complexity similar to that of a conventional m-sequence generator, which increases only linearly with the number of stages in the m-sequence generator. Our simulation results also show that the acquisition time of the proposed RSSE acquisition scheme is also linearly dependent on the number of stages in the m-sequence generator. Owing to the above properties, the employment of the proposed RSSE acquisition scheme is beneficial for the acquisition of long m-sequences. Index Terms--Acquisition, initial synchronization, maximum-likelihood (ML) estimation, m-sequence, pseudonoise (PN) signals, recursive decoding, sequential estimation, soft-in/soft-out (SISO) decoding, spread-spectrum signals.

In this letter, we extend our investigation of generalized multicarrier direct-sequence code-division multiple access by considering two additional types of chip waveforms, namely, the time-domain half-sine and raised-cosine chip waveforms, in addition to the rectangular chip waveform. A range of closed-form equations are provided for quantifying the effect of both the multipath interference and the multiuser interference, when using partially overlapping subcarriers. These closed-form formulas allow us to evaluate the bit-error rate performance of arbitrary code-division multiple access schemes using overlapping subbands with the aid of the standard Gaussian approximation. Index Terms--Code-division multiple access (CDMA), multicarrier, frequency-selective fading.

This paper investigates the first resource management problem for vehicular-to-infrastructure (V2I) networks under the in-band full-duplex (IBFD) backhauling scheme with guaranteed ultra-reliable and low-latency (URLLC) service. The considered networks suffers from interference caused by three node transmission in IBFD scheme and the mobility of vehicular user equipments (VUEs). The resource allocation problem is formulated to jointly optimize VUE association, resource block assignment (RA) and power allocation (PA), while satisfying the reliability and latency constraints at the same time. The formulated problem is a mixed integer non-linear problem with non-convex objective function and constraints. Finding globally optimal solution for this type of problem is still an open problem. To develop tractable solutions, the original problem is firstly simplified using derived equivalent expression for the objective function. The proposed method then decomposed it into RA and PA sub-problems. In each iteration, the PA sub-problem is solved for a set of given PA solution; while the solution for PA sub-problem is searched under determined RA results. The RA and PA sub-problems are solved iteratively until the converging condition is achieved. Theoretical analysis proves that the proposed method achieves Nash-stable equilibrium and local optimality for RA and PA sub-problems respectively. Simulation results verify the effectiveness of the derived performance analysis and demonstrate that the proposed algorithm outperforms the state-of-the-art algorithms in the literatures. [ABSTRACT FROM AUTHOR]

A class of generalized multicarrier direct sequence code-division multiple-access (MC DS-CDMA) schemes is defined and its performance is considered over multipath Nakagami-m fading channels. The spacing between two adjacent subcarriers of the generalized MC DS-CDMA is a variable, allowing us to gain insight into the effects of the spacing on the bit error rate (BER) performance of MC DS-CDMA systems. This generalized MC DS-CDMA scheme includes the subclasses of multitone DS-CDMA and orthogonal MC DS-CDMA as special cases. We present a unified analytical framework for determining the exact average BER of the generalized MC DS-CDMA system over generalized multipath Nakagami-m fading channels. The optimum spacing of the MC DS-CDMA system required for achieving the minimum BER is investigated and the BER performance of the system having optimum spacing is evaluated. The resultant BER is compared with that of both multitone DS-CDMA and orthogonal MC DS-CDMA.

In this paper we propose two novel low-complexity, low-delay erasure insertion schemes, namely, the output threshold test (OTT) and joint maximum output and ratio threshold Test (MO-RTT). The employment of the OTT and MO-RTT is beneficial in the context of the "errors-and-erasures" Reed-Solomon (RS) decoding in a slow frequency-hopping spread-spectrum (SFH/SS) system using M-ary frequency-shift keying (MFSK). The statistics of the erasure insertion related decision variables associated with the OTT, MO-RTT as well as with the ratio threshold test (RTT) are investigated, when the channel of each frequency-hopping (FH) slot is modeled as flat Nakagami-m fading. The transmitted signals also experience both additive white Gaussian noise (AWGN) as well as partial-band Gaussian interference (PBGI). The properties of these erasure insertion schemes are investigated with the aid of their statistics. The performance of the proposed erasure insertion schemes and that of the erasure insertion scheme using the RTT is investigated and compared in the context of RS coded SFH/SS systems using MFSK. Furthermore, the performance of the RS coded SFH/SS systems is also compared both with and without side-information concerning the PBGI. Index Terms--Errors-and-erasures decoding, frequency-hopping, joint maximum output and ratio threshold test, M-ary frequency-shift keying, Nakagami fading, output threshold test, partial band interference, ratio threshold test, Reed-Solomon codes, spread-spectrum communications.

A novel multiple-access scheme based on slow frequency-hopping multicarrier direct-sequence, code-division multiple access (SFH/MC DS-CDMA) is proposed and investigated, which can be rendered compatible with the existing second-generation narrow-band CDMA and third-generation wide-band CDMA systems. Blind joint soft-detection of the SFH/MC DS-CDMA signals is investigated, assuming that the receiver has no knowledge of the associated frequency-hopping (FH) patterns invoked. The system's performance is evaluated over the range of Nakagami multipath fading channels. The results show that blind joint soft-detection achieves the required bit-error rate performance, while blindly acquiring the FH patterns employed. This is advantageous during the commencement of communications or during soft handover. Index Terms--Blind detection, code-division multiple access, constant-weight codes, frequency-hopping, orthogonal frequency-division multiplexing.