Simultaneous Packet Transmissions Research Articles

Low-cost and high-performance channel access strategies for Internet of Nano-Things applications

Nanodevices, which are only a few nanometers (nm) in size, are interconnected to form the Internet of Nano-Things (IoNT) that performs complex operations. One of the key challenges is ensuring efficient channel access control for nanodevices, especially when dealing with large network sizes. Medium access control (MAC) protocols serve this purpose, but traditional approaches are not practical due to the inherent constraints of nanodevices. In this paper, we propose two novel MAC protocols for IoNT applications. The first protocol, Slot Assignment-Based (SAB) MAC, is a contention-free method relying on scheduling. In contrast to its counterparts, it enables simultaneous packet transmission through Time Spread On-Off Keying (TS-OOK), effectively minimizing the collision probability and end-to-end delay. The second protocol, Receiver-Initiated and Directed (RID) MAC, adopts a contention-based approach to reduce unnecessary transmissions caused by flooding. It achieves this by limiting the number of active nanodevices within a time interval using directional antennas without incurring scheduling overhead. We evaluated the performance of these protocols through comprehensive simulations, comparing them with counterparts in terms of packet transmission success, energy consumption, end-to-end delay and setup overhead. In dense topologies, SAB-MAC outperforms Transparent (TRN) MAC by approximately twice the packet transmission success reaching up to 95.73%. It accomplishes this with 1000 times lower end-to-end delay and reduced setup overhead than Time Division Multiple Access (TDMA). Conversely, RID-MAC achieves twice the packet transmission success of TRN-MAC and ten times that of unicast-based methods, all with lower end-to-end delay and nearly equivalent energy consumption. Consequently, due to its superior performance SAB-MAC is the optimal choice for communication between nanorouters (NRs). However, RID-MAC is more suitable for communication between nanosensors (NSs), as it incurs no setup overhead.

C-FD MAC: Constellation based Full-Duplex MAC protocol

Simultaneous transmission and reception of data packets in Full-Duplex (FD) communication can theoretically double the system throughput. However, efficient self-interference mitigation and symbol detection at the receiver is required to realize the full potential of FD communication in practical scenarios. In this paper, we propose a constellation-based FD medium access control (MAC) protocol (C-FD) for wireless local area networks (WLAN). In the proposed C-FD MAC protocol, the node and Access Point (AP) can exchange packets simultaneously by transmitting the symbols and using different modulation schemes. The superimposed constellation diagram has been used to decode the symbols efficiently at both ends. The novel feature of the C-FD MAC protocol is that it does not require any complicated interference cancellation techniques. The analytical results for Symbol Error Rate (SER), Packet Error Rate (PER), and throughput have been derived for the symmetrical and asymmetrical FD link considering the additive white Gaussian noise (AWGN) with Rayleigh fading. The proposed C-FD MAC protocol achieves nearly twice the throughput compared to Half duplex (HD) communication without compromising the SER. The analytical results have been validated with extensive simulation.

A path characteristics based adaptive subflow switching algorithm for dynamic heterogeneous MPTCP network

Multipath Transmission Control Protocol (MPTCP) can support simultaneous transmission of data packets over multiple paths, improve transmission reliability and aggregate network bandwidth to improve throughput. However, MPTCP cannot adjust the access state of subflows in real time according to the actual situation in the dynamic network, resulting in poor performance under the limitation of limited buffers. The existing path management algorithms, such as Fullmesh and PCDC, only select the subflows for concurrent transmission at the beginning, and cannot dynamically manage the subflow during the transmission. Therefore, we propose a path characteristics based adaptive subflow switching management (PASS) algorithm to manage multiple paths of MPTCP in real time and dynamically manage whether a subflow joins the transmission or not. Experimental results show that PASS is more stable and flexible than traditional Fullmesh algorithm and PCDC algorithm, and can obtain higher network throughput.

Simultaneous packet transmission (SPT) using multiple streams

A simultaneous packet transmission (SPT) technique is proposed to increase the throughput of a communication system. A SPT scheme employs multiple levels and employs multiple streams at each level above the first level. Every stream of the SPT has its assigned partition on the overall constellation. Symbols of an N-level SPT are formed by taking , bits from a selected stream of every level. The SPT scheme can employ higher code rates on streams at higher levels to increase the system throughput. Numerical results show that the SPT offers 15–30% throughput enhancement in turbo-coded LTE systems.

Cross-Networks Energy Efficiency Tradeoff: From Wired Networks to Wireless Networks

The tremendously large number of increasing Internet protocol (IP) packets call for quality of service (QoS) guaranteed packets transmission with low-delay, high throughput, and high energy efficiency (defined as the transmitted bits per unit energy consumption) in the fifth-generation (5G) networks. For this motivation, wavelength division multiplexing (WDM) networks and the next generation of wireless technologies are two major methods in the wired and wireless networks, respectively. However, the existing energy efficient switch fabric and wireless technologies have focused on either wired or wireless networks, only separately. The joint cross-networks optimization for energy efficiency in 5G remains unexplored. This does not fully facilitate the QoS guaranteed packets transmission and energy efficient networks planning from the viewpoint of cross networks. In this paper, we formulate a joint optimization model to enhance the performance of energy efficiency in 5G. In particular, each base station is equipped with a set of parallel tunable lasers for simultaneous transmission of multiple packets from the uplink users in the cell as well as the data center networks. We propose a novel joint cross-networks scheduling and routing (JCNSR) algorithm according to the wireless channel quality of users, user data rate, and the topology constraint. The IP packets are then delivered to the targeted cells via a transport layer in the WDM network and further transmitted to the targeted users via wireless channels under the constraint of delay. Based on the idea of the cross-networks tradeoff between the delay and the energy efficiency, JCNSR can achieve high-energy efficient transmission with performance guarantee. The effectiveness of the proposed framework is verified by extensive simulations.

A Three-way Handshaking Access Mechanism for Point to Multipoint In-band Full-duplex Wireless Networks

In-band Full-duplex (IBFD) wireless communication allows improved throughput for wireless networks. The current Half-duplex (HD) medium access mechanism Request to Send/Clear to Send (RTS/CTS) has been directly applied to IBFD wireless networks. However, this is only able to support a symmetric dual link, and does not provide the full advantages of IBFD. To increase network throughput in a superior way to the HD mechanism, a novel three-way handshaking access mechanism RTS/SRTS (Second Request to Send)/CTS is proposed for point to multipoint (PMP) IBFD wireless networks, which can support both symmetric dual link and asymmetric dual link communication. In this approach, IBFD wireless communication only requires one channel access for two-way simultaneous packet transmissions. We first describe the RTS/SRTS/CTS mechanism and the symmetric/asymmetric dual link transmission procedure and then provide a theoretical analysis of network throughput and delay using a Markov model. Using simulations, we demonstrate that the RTS/SRTS/CTS access mechanism shows improved performance relative to that of the RTS/CTS HD access mechanism.

Piggybacking assisted many-to-Many communication with efficient vehicle selection for improved performance in vehicular ad hoc networks

Vehicular Ad-hoc NETworks (VANETs) have lately gained the interest of researchers due to their unique properties of high mobility and constantly changing network topology. As mentioned in IEEE 802.11p which is the standard for VANETs, CSMA is used as the channel access mechanism. However, CSMA causes high contention and leads to lower network performance in terms of packet delivery ratio and average end-to-end delay. Many-to-Many (M2M) communication is a technique which makes use of simultaneous transmission of packets by using Code Division Multiple Access (CDMA). Although M2M communication helps to improve the performance of VANETs, further improvements can be done to fully reap the benefits of M2M communication. In this paper, we suggest piggybacking of information along with M2M communication in a vehicular network scenario. This leads to dissemination of more information from a vehicle at a time, thereby increasing the average packet delivery ratio and average end-to-end delay. Our simulation results confirm that piggybacking along with M2M communication helps to improve network performance in terms of packet delivery ratio and end-to-end delay. We mathematically analyse average packet delivery ratio and average end-to-end delay of such a system by modelling the buffers at vehicles and RSUs as M/M/1 and M/D/1 queues, respectively. Our analytical results are verified by extensive simulations. In M2M communication, vehicles are chosen randomly to enter in a communication session. In this paper, we formulate an optimization problem for selection of vehicles which can enter in a communication session and also propose an efficient vehicle selection algorithm for the same. Our proposed algorithm not only improves the average packet delivery ratio and average end-to-end delay of the network but also significantly reduces the number of packets dropped in the network.

Performance Analysis of CSMA/CA based Medium Access in Full Duplex Wireless Communications

Full duplex communication promises a paradigm shift in wireless networks by allowing simultaneous packet transmission and reception within the same channel. While recent prototypes indicate the feasibility of this concept, there is a lack of rigorous theoretical development on how full duplex impacts medium access control (MAC) protocols in practical wireless networks. In this paper, we formulate the first analytical model of a CSMA/CA based full duplex MAC protocol for a wireless LAN network composed of an access point serving mobile clients. There are two major contributions of our work: First, our Markov chain-based approach results in closed form expressions of throughput for both the access point and the clients for this new class of networks. Second, our study provides quantitative insights on how much of the classical hidden terminal problem can be mitigated through full duplex. We specifically demonstrate that the improvement in the network throughput is up to 35-40\% over the half duplex case. Our analytical models are verified through packet level simulations in ns-2. Our results also reveal the benefit of full duplex under varying network configuration parameters, such as number of hidden terminals, client density, and contention window size.

Frequency-Domain Backoff Mechanism for OFDM-Based Wireless LANs

Modern wireless communication technologies enabled high data rate support which stands in need of proficient MAC protocols. In WLANs, the fair channel access and collision avoidance are achieved by employing contention. The contention period degrades bandwidth utilization and longer delays; the network performance worsens for high data rates. Previously, this problem is addressed by modifying or adaptively selecting contention time using the same time-domain- based backoff mechanism. In this paper, we propose a backoff scheme, FD-Backoff, in which backoff is taken in the frequency domain. Therein, an integer is assigned to every data subcarrier, and then, a random data subcarrier (integer) is chosen to transmit a RTS packet. Since OFDM-based data subcarriers are orthogonal, thus simultaneous transmission of multiple RTS packets is possible. Every nontransmitter node listens on the whole channel bandwidth to observe any active subcarriers. The transmitter who chose smallest subcarrier for RTS transmission wins channel access and receiver replies it with a CTS packet. Contrary to the IEEE 802.11 backoff mechanism, the proposed backoff scheme offers lesser and relatively fixed contention overhead. Performance analysis based on analytical and simulation study suggests that the proposed scheme promises lower contention overhead and higher efficiency gain (up to 35 %) as compared to standard channel access mechanism.

An efficient scheduling scheme for hybrid TDMA and SDMA systems with smart antennas in WLANs

Smart antennas are an emerging technology that exploits spatial diversity and allows an access point (AP) to simultaneously transmit downlink packets to multiple stations (STAs). In this paper, we propose a new AP scheduling scheme for hybrid TDMA (Time Division Multiple Access) and SDMA (Spatial Division Multiple Access). Our scheduling scheme aims at maximizing the system throughput while maintaining the fairness among STAs and guaranteeing Quality of Service of different traffic classes. The original contributions of our scheduling scheme include: (1) We propose a transmission framework that allows TDMA STAs to transmit in the TDMA fashion, and non-TDMA STAs to compete channel access in the CSMA/CA fashion. (2) We analyze the performance of CSMA/CA STAs and determine the optimal contention window size for each STA to minimize the collision rate subject to the contention period constraint. (3) We propose an analysis to determine the minimal length of time allocated to non-TDMA STAs during a transmission period such that each STA will have a success transmission probability above a specified threshold in each period. (4) We propose a scheduling algorithm that schedules simultaneous packet transmission to multiple STAs such that maximal number of packets can be transmitted to multiple STAs without causing unacceptable interference.

MIMO-Assisted MPR-Aware MAC Design for Asynchronous WLANs

The use of multiple-packet reception (MPR) in wireless networks is known to improve throughput especially in high-traffic conditions. The lack of synchronization among the nodes in random access systems introduces significant challenges toward the adoption of MPR in the PHY and the MAC design for systems using MPR. In this paper, we propose an asynchronous MPR method for the PHY and also design a compatible random access MAC for wireless local area networks (WLANs). Relying on space-time coding techniques, our MPR method detects multiple asynchronous packets while providing diversity and low bit error rates at the PHY layer. Extending the design of IEEE 802.11, our MPR MAC design encourages simultaneous packet transmissions and handles multiple packet receptions. Simulation results show that the throughput of a WLAN significantly improves in many scenarios of operation using our proposed PHY/MAC MPR framework.

Multicast capacity of optical ring network with hotspot traffic: The bi-directional WDM packet ring

Packet-switching WDM ring networks with a hotspot transporting unicast, multicast, and broadcast traffic are important components of high-speed metropolitan area networks. For an arbitrary multicast fanout traffic model with uniform, hotspot destination, and hotspot source packet traffic, we analyze the maximum achievable long-run average packet throughput, which we refer to as multicast capacity, of bi-directional shortest path routed WDM rings. We identify three segments that can experience the maximum utilization, and thus, limit the multicast capacity. We characterize the segment utilization probabilities through bounds and approximations, which we verify through simulations. We discover that shortest path routing can lead to utilization probabilities above one half for moderate to large portions of hotspot source multi- and broadcast traffic, and consequently multicast capacities of less than two simultaneous packet transmissions. We outline a one-copy routing strategy that guarantees a multicast capacity of at least two simultaneous packet transmissions for arbitrary hotspot source traffic.

Wireless mesh network security: A traffic engineering management approach

The wireless mesh network (WMN) is an emerging multihop, heterogeneous, easily scalable and low cost network. The architecture of the WMN is a connectionless-oriented, mobile and dynamic traffic of routed packets. The mesh infrastructure environment easily forms multiple chains of wireless LANs (WLAN) coupled with the simultaneous multihop transmission of data packets from peripherals via mobile gateways to the wireless cloud. WMN operates as an access network to other communication technologies. This exposes the WMN to numerous security challenges not only in the mesh transmission operation security but also in the overall security against foreign attacks. We surveyed and identified the security vulnerabilities in Internet Protocol (IP) broadband networks, the security challenges in the routing layer of the WMN and explored new concepts to solving security challenges in WMN using traffic engineering (TE) security resolution mechanisms. We analyzed the advantages, comparative strengths and weakness in the use of traffic engineering based on simulation results and evaluations.

Optimal Scheduling Method in MIMO WLAN with Distributed Coordination Function

This paper addresses the optimal number of simultaneous data transmissions that maximize the system throughput in an MIMO WLAN. To facilitate simultaneous packet transmissions, both transceivers have to exchange preambles to calculate the channel state information. This exchange is combined with the RTS (request to send)/CTS (clear to send) handshake which is used to contend for the channel in WLANs. This study presents an expression for the optimal number of simultaneous data transmissions under the distributed coordinate function mechanism derived using the Markov chain model, as well as an analytical formula for the optimal system throughput given the length of the contention window and the number of nodes in the network. The analytical results show that the system throughput cannot be enhanced by simply increasing the number of simultaneous data transmissions.

Performance Improvement of Routing Protocol in Ad-hoc Networks Using Smart Antenna with Balance Load

We have presented a balanced routing protocol for Mobile Ad-hoc Networks using the smart antenna in this paper. Multipath routing can be effectively used to maximize the utilization of network resources for real-time traffic. In mobile ad-hoc network, this approach can suffer from co-channel interference or route coupling due to simultaneous transmission of packets via multiple routes. We use zone-disjoint routes and define maximally zone disjointness as route selection criteria. An adaptive routing strategy is proposed that use the advantages of directional antennas in ad hoc networks through the selection of maximally zone disjoint routes. Zone-disjoint routes would reduce the route coupling effect in wireless media by selecting routes in such that it produce minimal interference among communication over multiple routes. The proposed routing protocol provide effective load balancing in wireless media and it is implemented for both single path and multipath routing on ad hoc networks with directional antennas. Simulation results show that zone-disjoint single path routing can produce better throughput compare to multipath and AODV (Ad-hoc on-demand distance vector) routing protocol for more number of simultaneous communications.

Multichannel Mobile Ad Hoc Links for Multimedia Communications

This paper is mainly concerned with multichannel transmission of real-time information such as video over multihop ad hoc links. We propose two multichannel routing protocols. The first is based on single-path routing and aims at suppressing the intrapath interference in a carrier sense multiple access/collision avoidance network. This is achieved by developing a link-partitioning scheme where nodes in the neighboring partitions operate at different nonoverlapping frequency bands. For this approach, we present a systematic channel assignment technique that has been specifically developed for the ad hoc on-demand distance vector routing protocol. It is shown that this partitioning scheme can considerably enhance the throughput performance of a multihop link. The second multichannel scheme is developed for transmission of real-time traffic over multiple-path routes. Bear in mind that multiple-path diversity routing has been shown to be very effective in dealing with network congestion in wireline Internet protocol networks. Unfortunately, in mobile ad hoc network environments, particularly for real-time traffic, this approach can suffer greatly from cochannel interference due to the simultaneous transmission of packets via multiple routes. In this respect, we have designed a dual-path routing protocol, which guarantees a different frequency band for each path, thus eliminating any interpath interference. We show that this protocol has an important property, which is reducing the probability of losing both routes at the same time. Based on this important property, we demonstrate that a combination of the routing protocol and dual-description video coding can greatly enhance the ad hoc network performance of video transmission for real-time traffic.

Multicast Capacity of Optical Packet Ring for Hotspot Traffic

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> Hotspot traffic is common in metro ring networks connecting access networks with backbone networks, and these metro rings are also expected to support a mix of unicast, multicast, and broadcast traffic. Shortest path (SP) routing, as employed in the IEEE 802.17 Resilient Packet Ring (RPR), is widely considered for metro rings as it maximizes spatial reuse and, thus, the achievable packet throughput (capacity) for uniform traffic. In this paper, we analyze the capacity of bidirectional optical ring networks, such as RPR, employing SP routing for multicast (nonuniform) hotspot traffic (whereby unicast and broadcast are considered as special cases of multicast). We find that, when the traffic originating at the hotspot exceeds a critical threshold, then SP routing leads to substantial reductions in capacity to a value close to one simultaneous packet transmission. To overcome this limitation of SP routing, we propose a simple combined SP/one-copy routing strategy that provides a capacity of at least two simultaneous packet transmissions. </para>

Approximate performance analysis of heavily loaded slotted downlink channel in a wireless CDMA system supporting integrated voice/data services

This paper is concerned with the performance analysis of a slotted downlink channel in a wireless code division multiple access (CDMA) communication system with integrated packet voice/data transmission. The system model consists of a base station (BS) and mobile terminals (MT), each of which is able to receive voice and/or data packets. Packets of accepted voice calls are transmitted immediately while accepted multipacket data messages are initially buffered in first in, first out (FIFO) queues created separately for each destination. The BS distinguishes between silence and talkspurt periods of voice sources, so that packets of accepted data messages can use their own codes for transmission during silent time slots. To fulfill QoS requirements for both traffic types, the number of simultaneous packet transmissions over the downlink channel must be limited. To perform this task, a fair, single-priority multiqueueing scheduling scheme is employed. Discrete-time Markov processes are used to model the system operation. Statistical dependence between queues is the main difficulty which arises during the analysis. This dependence leads to serious computational complexity. The aim of this paper is to present an approximate analytical method which enables one to evaluate system performance despite the dependence. Therefore, it is assumed that the system is heavily loaded with data traffic, and a heuristic assumption is made that makes the queueing analysis computationally tractable. Typical system performance measures (i.e., the data message blocking probability, the average data throughput and delay) are evaluated, however, due to the accepted heuristic assumption, the analysis is approximate and that is why computer simulation is used to validate it.

A Generalized Analytical Framework for SMPT in a Multicode CDMA Wireless System

Simultaneous MAC Packet Transmission (SMPT) has recently been proposed for stabilizing the throughput over wireless links, which is one of the key challenges in providing high-quality wireless multimedia services. SMPT stabilizes the wireless link by transmitting multiple packets on multiple CDMA channels in parallel in response to packet drops due to wireless link errors. These parallel packet transmissions stabilize the link layer throughput, but they also increase the interference level in a given cell of a cellular network or cluster of an ad-hoc network, which in turn reduces the number of traffic flows that can be simultaneously supported in a cell/cluster. We have recently developed an analytical framework for the class of SMPT mechanisms for a simple Bernoulli packet generation process, which does not reflect the oftentimes bursty packet generation processes encountered in real networks. In this paper we develop a generalized analytical framework for SMPT, which accommodates bursty packet traffic (and also non-bursty Bernoulli traffic). This framework expresses the system dynamics in transition probabilities for a Markov chain and calculates the effects of the interference through an iterative approach. The numerical results from our analytical framework and verifying simulations indicate that SMPT provides a significant reduction in packet loss and buffer occupancies (and delay), especially for persistent traffic bursts, in exchange for a reduced number of supported flows. Our analytical framework quantifies these system trade-offs with good accuracy and can thus be employed for resource management.

Wireless video streaming with TCP and simultaneous MAC packet transmission (SMPT)

AbstractVideo streaming is expected to account for a large portion of the traffic in future networks, including wireless networks. It is widely accepted that the user datagram protocol (UDP) is the preferred transport protocol for video streaming and that the transmission control protocol (TCP) is unsuitable for streaming. The widespread use of UDP, however, has a number of drawbacks, such as unfairness and possible congestion collapse, which are avoided by TCP. In this paper we investigate the use of TCP as the transport layer protocol for streaming video in a multi‐code CDMA cellular wireless system. Our approach is to stabilize the TCP throughput over the wireless links by employing a recently developed simultaneous MAC packet transmission (SMPT) approach at the link layer. We study the capacity, i.e. the number of customers per cell, and the quality of service for streaming video in the uplink direction. Our extensive simulations indicate that streaming over TCP in conjunction with SMPT gives good performance for video encoded in a closed loop, i.e. with rate control. We have also found that TCP is unsuitable (even in conjunction with SMPT) for streaming the more variable open‐loop encoded video. Copyright © 2004 John Wiley &amp; Sons, Ltd.