Game Theoretic Approaches for Multiple Access in Wireless Networks: A Survey

The standard time division multiple access (TDMA) cellular network is designed so that physically adjacent cells are assigned different frequency bands, or channels, in order to reduce inter-cell interference. A multiple-access scheme is presented in which TDMA is used inside each cell, but different transmitted pulse shapes with low cross-correlations are assigned to adjacent cells. These pulses could be direct-sequence spread-spectrum pulses, which have been proposed for code division multiple access (CDMA) wireless networks. Such a hybrid system combines the high intra-cell capacity of TDMA with the inter-cell and multipath interference rejection capabilities of CDMA. It is concluded that this hybrid scheme offers a potential increase in capacity relative to intra-cell TDMA/inter-cell frequency-division multiple access (FDMA) provided that interference suppression techniques can be used to suppress inter-cell interference. Additional advantages and disadvantages of the scheme are discussed.

Communication networks beyond 3G will see the interconnection of heterogeneous radio access networks in order to always provide the best quality of service in the most efficient way to users with multi-mode terminals. This scenario poses a number of critical issues, which have to be faced in order to get the best from the integrated network. In this paper we investigate the issue of parallel transmission over multiple radio access networks: in particular we propose simple but effective radio resource management algorithms, whose performance is investigated by means of a simulative approach in UMTS-IEEE802.11a and IEEE802.16e-IEEE802.11a heterogeneous networks (adopted as case studies). An insight on TCP level critical aspects, strictly related to the parallel transmission over multiple access networks, is also provided.

Rate splitting multiple access (RSMA) is a promising approach that has gained momentous attention in the field of wireless communications. With the increasing demand for higher data rates and reliable connections, traditional multiple access approaches like SDMA, NOMA have limitations in terms of interference management as well as channel state information uncertainty. The effectiveness of the RSMA has been recognized in addressing these limitations and providing improved performance in multi-antenna systems. RSMA ruptures user messages into common as well as private parts – the common part is decoded by all users to mitigate interference while the private part is decoded only by the intended user. This bridges orthogonal and non-orthogonal multiple access schemes. Benefits of RSMA include optimal performance in many scenarios, robustness against imperfect CSIT, lower feedback overhead and complexity compared to alternatives. RSMA has many potential applications in 6G use cases like mMTC, URLLC, V2X, and integrated sensing-communications. Ongoing research is still needed, especially on implementation and standardization. The current study focuses on the notion of rate splitting, the benefits of RSMA, working principle of RSMA, implementation challenges, RSMA's implementation in 5G and beyond, a comparison with other multiple access techniques, as well as its problems and future trends in wireless networks.

Due to constraints inherent in RF systems, it is commonly agreed that collision detection is not feasible for CSMA-based wireless networks. However, by applying ideas from the busy-tone solution for hidden terminals and engineering together existing solutions for RF communications, we devise a simple method to reliably detect collisions for the wireless channel. We investigate the throughput gain delivered by CSMA/CD and its cross-layer designed version for multipacket-reception capable physical layers. We show that collision detection can help the system operate closer to its channel capacity. Our novel performance-improving protocols can be applied as beneficial extensions to the IEEE 802.11 wireless LAN standards

Direct sequence spread spectrum (DSSS) is a state-of-the-art technology evolved over the last 3–4 decades. The inherent features of DSSS such as anti-jamming, multiple access, low probability of intercept (LPI) and above all ease of deployment makes it an ideal transmission scheme for defense as well as commercial applications. Most of the modern remote control units (RCUs control small UAVs or helicopter, send command and control data using DSSS as a standard technique. As the number of users or aircraft to control increase, the DSSS alone may not be sufficient enough to provide multiple accesses. Therefore, a hybrid approach should be opted by using another multiple access scheme such as time division multiple accesses (TDMA) in conjunction with DSSS to obtain an efficient multiple accesses. Other multiple access schemes such as Frequency Division Multiple Access (FDMA) can also be used. However, they require more resources such as frequency and require broadband RF front ends. Hence, TDMA with DSSS is a viable solution. The hybrid form allows to transmit data in a collision-free manner and takes advantage of the broadband property of DSSS. This paper implements the IEEE 802.11b standard DSSS and makes it hybrid with TDMA by designing a complete frame structure and finds the BER performance results of the final design. The results of BER are simulated at different spreading factors of codes by using MATLAB.

Energy Efficient Scheduling on Hybrid Multiple Access at Backend of FiWi

Reconfigurable intelligent surface (RIS) has recently been envisioned to provide an adaptable channel for futuristic wireless communication networks. This work characterized the impact of hardware impairments in the downlink RIS-aided non-orthogonal multiple access (NOMA) wireless networks. We considered the hardware impairments in the transceivers of the base station (BS) and users, phase error at the RIS and the imperfect successive interference cancellation (SIC) for the NOMA users. Specifically, the performance is evaluated by deriving the closed-form expressions for the outage probability (OP), spectral efficiency (SE) and energy efficiency (EE). Additionally, the performance of the orthogonal multiple access (OMA) system is also evaluated and compared with its NOMA counterpart. The RIS-aided NOMA outperforms OMA for the ideal hardware scenario. However, the hardware impairments significantly deteriorate RIS-aided NOMA's performance compared to RIS-aided OMA. Further, we have also compared the proposed RIS-aided NOMA with the baseline full-duplex relaying (FDR) based NOMA. The results show that the gains are more significant for a RIS-aided system than FDR.

The gateways are the performance bottleneck of wireless mesh access networks and thus alleviating stress on them is essential to making such wireless networks robust and scalable. Using proxy servers or wireless peer-to-peer streaming techniques can help reduce the gateway load. However, these techniques, because they are data caching methods, do not save wireless resources. We instead consider a communication-sharing approach in this paper. Traditional stream sharing solutions depend on cooperation with the video server. However, in the wireless access network it is difficult to cooperate with online video sites. To address this problem in wireless mesh access networks, we propose a distributed video sharing technique called Dynamic Stream Merging (DSM). DSM is able to improve the robustness of the access network without cooperation from the online video site or the users and has the intelligence to handle sudden spikes in demand for certain videos due to specific events, thereby preventing adverse effects to other daily wireless traffic. The technique can also leverage the 80:20 data access pattern, common for many video applications, to substantially increase the service throughput. We explain the DSM technique, present the system prototype, and discuss the experimental results.

Orthogonal Frequency-Division Multiple Access (OFDMA) systems have attracted considerable attention through technologies such as 3GPP Long Term Evolution (LTE) and Worldwide Interoperability for Microwave Access (WiMAX). OFDMA is a flexible multiple-access technique that can accommodate many users with widely varying applications, data rates, and Quality of Service (QoS) requirements. OFDMA has the advantages of handling lower data rates and bursty traffic at a reduced power compared to single-user OFDM or its Time Division Multiple Access (TDMA) or Carrier Sense Multiple Access (CSMA) counterparts. In our work, we propose a Particle Swarm Optimization based resource allocation and scheduling scheme (PSORAS) with improved quality of service for OFDMA Systems. Simulation results indicate a clear reduction in delay compared to the Frequency Division Multiple Access (FDMA) scheme for resource allocation, at almost the same throughput and fairness. This makes our scheme absolutely suitable for handling real time traffic such real time video-on demand.

We consider a mobile network consisting of both the wireless access network and the backhaul network. All base stations in the access network and gateways in the backhaul network are equipped with caches, so that routing costs for serving content requests can be reduced by caching the requested content items closer to the users. In this case, user association in the wireless access network must be aware of both the quality of wireless channels and the content caching strategy. In this paper, we propose a framework that jointly optimizes wireless user association and content caching in both access and backhaul networks. The resulting problem is NP-hard. We propose a polynomial-time algorithm based on convex approximation and pipage rounding that produces a solution within a constant factor of 1 − 1/e from the optimal. Simulation results show that the proposed joint algorithm outperforms schemes that combine cache-independent user association methods with traditional caching strategies (e.g. LRU) in terms of minimizing the aggregate routing cost and backhaul traffic while achieving a high data sum rate in the access network.

5G-Flow: A unified Multi-RAT RAN architecture for beyond 5G networks

Wireless networks have become a very attractive solution for soft real-time data transport in the industry. For such technologies to carry real-time traffic, reliable bounds on end-to-end communication delays have to be ascertained to warrant a proper system behavior. As for legacy wired embedded and real-time networks, two main wireless multiple access methods can be leveraged: one is time division multiple access (TDMA), which follows a time-triggered paradigm, and the other is carrier sense multiple access with collision avoidance (CSMA/CA), which follows an event-triggered paradigm. This paper proposes an analytical comparison of the time behavior of two representative TDMA and CSMA/CA protocols in terms of the worst-case end-to-end delay. This worst-case delay is expressed in a probabilistic manner because our analytical framework captures the versatility of the wireless medium. Analytical delay bounds are obtained from delay distributions, which are compared to fine-grained simulation results. Exhibited study cases show that TDMA can offer smaller or larger worst-case bounds than CSMA/CA depending on its settings.

For future mobile communications, an appropriately chosen multiple access scheme is a critical issue. To support robust frequency planning, multi-operator scenarios, system coexistence and hierarchical cell structures, frequency division multiple access (FDMA) and multicarrier techniques are viable choices. Further multiple access schemes presently under discussion are code division multiple access (CDMA) and time division multiple access (TDMA). A mobile radio system concept deploying a hybrid frequency and time divided code division multiple access (F/T/CDMA) scheme with a multicarrier CDMA (MC-CDMA) component, called MC/JD-CDMA, is proposed and performance results for the uplink are presented. Attractive features of the proposed system concept are the possibility to flexibly offer voice and data services with different bit rates, soft capacity, as well as inherent frequency and interferer diversity.

The proliferation of mobile demands and increasingly multifarious services pose challenges to both the radio access networks (RANs) and the core network (CN). Unfortunately, the traditional networks can hardly meet the increasing requirements. Software-defined network (SDN) and network virtualization (NV) are considered as innovative paradigms to stress these problems. By extending SDN to wireless networks, software-defined wireless network (SDWN) consisting of both RANs and CN can be obtained. In this paper, the RANs and CN of SDWN are virtualized to virtual access points (VAPs) and network slices respectively based on NV technology. Considering the system scenario that a SDWN consists of overlapping RANs, an optimal joint VAP and network slice selection scheme is proposed. To characterize the complicated transmission performance of VAPs and network slices, the concepts of utility function and network calculus are introduced, and the joint utility of VAPs and network slices is formulated based on which the optimal VAP and network slice combination corresponding to the maximal joint utility can be selected. The simulation results demonstrate the efficiency of the proposed scheme.

We study the problem of user clustering and power assignment for a network comprised of cellular users and underlay device-to-device (D2D) users operating under a non-orthogonal multiple access (NOMA) scheme. Our goal is to maximize the sum-rate of the network by jointly optimizing the user clustering and power assignment. Moreover, we also aim to provide interference protection for the cellular users. The formulated optimization problem is a mixed-integer non-convex problem. Thus, the original problem is decomposed into two subproblems. The first subproblem of user clustering is formulated as a matching game with externalities, where this matching game is solved sequentially while the second subproblem pertaining to power assignment is solved using complementary Geometric programming. Finally, an efficient joint iterative algorithm is proposed that can achieve a suboptimal solution for the mix integer non-convex NP-hard problem. Simulation results show that the proposed algorithm can achieve up to 70% and 92% of performance gains in terms of the average sum-rate in comparison with the general NOMA and traditional orthogonal frequency-division multiple access (OFDMA) schemes, respectively. Moreover, our results show that the proposed scheme significantly enhances the network connectivity in terms of the number of admitted users compared with the traditional OFDMA, NOMA, and D2D schemes.