Performance Analysis of LTE-LAA Network

To meet the dramatically increasing traffic demand, licensed-assisted access (LAA) has been proposed for long-term evolution (LTE) systems to operate on the unlicensed spectrum. However, it is a huge challenge to achieve fair and efficient coexistence between LAA and Wi-Fi on the same band. In this paper, we devise a novel channel access approach for LAA eNBs to improve system throughput and achieve fair coexistence with Wi-Fi nodes. Specifically, Carrier Sense Multiple Access with Enhanced Collision Avoidance (CSMA/ECA), which is able to reach and maintain collision-free operation by deterministic backoff (DB) after successful transmissions, is introduced to the listen-before-talk (LBT) procedure of LAA eNBs to improve the coexistence system throughput. However, note that the fixed DB value in traditional CSMA/ECA cannot ensure fair coexistence all the time corresponding to different network sizes. Therefore, an adjustable DB value scheme is devised to replace the fixed one, in order to achieve fair coexistence whatever the number of Wi-Fi nodes and LAA eNBs is. Aiming to obtain the maximum system throughput improvement, the behavior of a LAA eNB is modeled as a Markov chain, and the throughput of the coexistence network is derived. Then, we formulate a throughput optimization problem and develop an algorithm of DB value adjustment, which can not only achieve the maximum throughput improvement but also maintain the fair coexistence whatever the number of nodes in the coexistence network is. At last, numerical results are presented which validate the accuracy of our analysis model and demonstrate the effectiveness of the proposed algorithm.

Licensed Assisted Access (LAA) is considered one of the latest groundbreaking innovations to provide high performance in future 5G. Coexistence schemes such as Listen Before Talk (LBT) and Carrier Sensing and Adaptive Transmission (CSAT) have been proven to be good methods to share spectrums, and they are WiFi friendly. In this paper, a modified LBT-based CSAT scheme is proposed which can effectively reduce the collision at the moment when Long Term Evolution (LTE) starts to transmit data in CSAT mode. To make full use of the valuable spectrum resources, the throughput of both LAA and WiFi systems should be improved. Thus, a two-layer Coalition-Auction Game-based Transaction (CAGT) mechanism is proposed in this paper to optimize the performance of the two systems. In the first layer, a coalition among Access Points (APs) is built to balance the WiFi stations and maximize the WiFi throughput. The main idea of the devised coalition forming is to merge the light-loaded APs with heavy-loaded APs into a coalition; consequently, the data of the overloaded APs can be offloaded to the light-loaded APs. Next, an auction game between the LAA and WiFi systems is used to gain a win–win strategy, in which, LAA Base Station (BS) is the auctioneer and AP coalitions are bidders. Thus, the throughput of both systems are improved. Simulation results demonstrate that the proposed scheme in this paper can improve the performance of both two systems effectively.

Long Term Evolution (LTE) in unlicensed spectrum, Licensed Assisted Access (LAA), has been considered as an effective complement in offloading growing traffic. The LAA is expected to be deployed initially through the small cell integrated under LTE macro cell. Therefore, LTE users under the coverage of LAA small cell must decide to connect one of the co-located networks either LTE or LAA to maximize their performance. In this scenario, we model a network selection game for LTE users using mixed strategy game theoretic approach. Afterwards, we formulate behavior of strategic users toward network selection as a function of the number of nearby users. The simulation results show that increasing number of nearby users make a user less likely to switch to LAA small cell. Additionally, more users nearby make it less likely that LAA resources is being utilized.

WBAN을 위한 MAC 프로토콜은 의료용 센서 노드의 가변적인 데이터를 효율적으로 처리하기 위해서 응급상황에서 발생하는 트래픽을 가장 높은 우선순위로 처리하는 CSMA/CA(: Carrier Sense Multiple Access with Collision Avoidance) 알고리즘을 수행하게 된다. 노드가 전송하는 응급 메시지는 충돌이 발생하게 되고 응급 메시지 재전송으로 인한 전송 지연이 발생할 수 있으며 재전송으로 인한 에너지 낭비를 가져올 수 있다. 본 논문에서는 이러한 문제점들을 개선하기 위해서 우선순위 큐잉을 적용한 CSMA/CA 알고리즘의 경우 MAC 명령어 프레임과 데이터 프레임의 우선순위를 정하여 서로 다른 백오프 파라미터를 적용하고 충돌로 인한 프레임 손실을 최소화하는 알고리즘을 제안하였다. 성능평가 결과 제안한 MAC 프로토콜을 사용했을 때가 IEEE 802.15.6을 사용했을때 보다 충돌 확률이 감소하여 패킷 전송 처리율이 증가하고 패킷 손실량이 감소함을 보였다. MAC protocol for WBAN performs CSMA/CA(:Carrier Sense Multiple Access with Collision Avoidance)algorithm that handles traffic which occurs in emergency with top priority in order to deal with variable data of sensor node for medicine. Emergency message that node sends undergoes collision and delay of transmission by retransmission of emergency message and waste of energy by retransmission. This paper suggests algorithm that minimizes loss of frame caused by collision and applies different backoff parameters by setting order of priority between MAC instruction frame and data frame in CSMA/CA algorithm case which applies order of priority queuing to improve aforementioned problem. According to performance evaluation, it has been found that using suggested MAC protocol showed lower collision probability, higher packet transmission processing ratio and lower packet loss compared with using IEEE 802.15.6.

Long Term Evolution (LTE)-License Assisted Access (LAA), which leverages unlicensed resource sharing with the Wi-Fi network, is a promising technique to address the spectrum scarcity issue in present and future wireless networks. However, unlicensed spectrum sharing between Wi-Fi and LAA requires fair resource allocation with specific performance guarantees for both sets of Wi-Fi and LAA stations. In this paper, an optimal communication policy is devised for LAA stations coexisting on a single unlicensed channel with Wi-Fi stations. The inter-network collisions are avoided through non-overlapping transmission phases for Wi-Fi and LAA networks. The throughput performance of LAA network is maximized while guaranteeing a proportionally fair performance among LAA stations and a fair share for Wi-Fi stations. The proposed scheme, unlike the state-of-the-art coexisting mechanism, jointly optimizes the transmission probability and the transmission rate for each LAA station. The formulated optimization problem to maximize network throughput is solved analytically. The numerical results demonstrate a significant improvement in the LAA throughput, more than 75%, as compared to the case when transmission probabilities are not optimized. Moreover, a notable gain of 8-9% in the fairness index reflects the intra-network fairness of the proposed LAA network over the conventional LAA network.

Licensed-Assisted Access (LAA) using Long Term Evolution (LTE) is a promising technique to extend the available bandwidth by aggregating the unlicensed spectrum. To guarantee fair co-existence of nodes deployed by different operators and different RATs, listen-before-talk (LBT) mechanism and carrier selection can be adopted by LAA as efficient candidates. In this paper, we provide insight into the LBT based LAA networks deployed by multiple operators using a hard core point process (HCPP) model. Moreover, an adaptive carrier selection scheme is developed where neighboring small cells select different carriers to avoid blocking each other so that larger number of active small cells can be retained after LBT channel sensing. The analytical results are developed in terms of active probability and coverage probability for single carrier, random carrier selection and the adaptive carrier selection scheme. It is revealed by numerical results that the number of active small cells can be significantly increased by employing adaptive carrier selection especially for large number of carriers, which further improves the network throughput.

The current stage of telecommunication technologies development is characterized by the rapid growth use of wireless technologies in access networks and the growth requirements for its quality. The bottleneck that significantly reduces the bandwidth of each subscriber connection is that the total bandwidth of the wireless local network is shared among its active members by the shared technology used. The access management sub-layer to the shared physical environment is responsible for this in the network architecture. The main method used at this sub-layer is the Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) scheme. This work is devoted to the analysis of CSMA/CA scheme and the development of an analytical model for its further study and use for the improvement of wireless local networks. The input data is a transition state diagram of a local area wireless network station in data transmission mode. According to the CSMA/CA scheme, stations cannot change their state after starting frame transmission until a confirmation frame of successful reception arrives from the addressee or until the time to wait for it expires. Considering this, it is proposed to use a simplified transition state diagram for the analysis. The operation of the station by the simplified transition state diagram is described using a system of differential equations. As a result of the solution of this system, expressions representing the probability of the station being in each of its states as a function of the intensities of the station’s transitions from each state to another are derived. The values of these intensities depend on both the outgoing traffic of the station and the traffic in the network. The resulting expressions can be used in further work on the analysis of the CSMA/CA scheme, as they make it possible to estimate the operation of the station at different ratios of the station’s output traffic and external traffic generated by other stations of the network. This can be used to develop an enhanced algorithm station operation of wireless local area networks by adapting the parameters of the CSMA/CA scheme to specific current loads of both the station and the network.

Licensed-Assisted Access (LAA) which allows LTE to be deployed in unlicensed spectrum is a promising technique currently under standardization in 3GPP Rel-13. To guarantee a peaceful coexistence of LAA with the incumbent systems such as WiFi, listen-before-talk (LBT) which requires the node to sense the medium before data transmission is introduced. On the other hand, LBT also prevents simultaneous transmission from neighbouring nodes of the same LAA operator. In order to increase the spectral efficiency of LAA, frequency reuse for transmission by neighbouring nodes of the same operator has been agreed to be one target of LAA design. In this paper we evaluate the performance of LAA in an indoor scenario assuming both one and two LAA networks deployed by different operators. It is shown that LBT is indeed needed to ensure good performance with multiple LAA operators, especially at high load. And frequency reuse between neighbouring nodes of the same LAA operator can further improve the performance.

The effectiveness of wireless local area networks significantly depends on the method of access to the common physical environment. The main access method that is used today in wireless local area networks is carrier sense multiple access with collision avoidance (CSMA/CA), managing the efficient distribution of the common environment between active stations. In this paper, as a topic of research we consider the state transition diagram of a CSMA/CA - based network, and we describe it by a system of differential equations. Analytical expressions for the probabilities of being in one of the possible states of a network station are derived.KeywordsWireless local computer networkCarrier sense multiple access with collision avoidance (CSMA/CA)State transition diagram

In this paper we present a two-dimensional medium access control (MAC) protocol. Orthogonal frequency division multiple access (OFDMA) can make multiple stations (STA) transmit simultaneously on different sub-channels. On the other hand, carrier sense multiple access with collision avoidance (CSMA/CA) could make different stations contend the available channel from the time domain to avoid collision with each other. We propose a two-dimensional MAC protocol based on OFDMA and CSMA/CA in broadband systems. With the new designed MAC protocol different stations will access the channel from the time-frequency domain without interference and collision. The combination of OFDMA with CSMA/CA will improve the system throughput with efficient MAC and decrease the collision probability. We design that different stations will contend the available time-frequency resources dynamically under fairness. The system throughput of the designed protocol is analyzed and simulation results are presented to show the performance under our designed protocol far better than the conventional CSMA/CA protocol.

Reader to reader collision is a common problem in Radio Frequency Identification (RFID) networks where are large number of RFID readers are present close to each other. Motion of readers can further cause difficulty in reading of tags. Evaluation and comparison of anti-collision algorithms must be done using simulation tools specifically designed for the same rather than general purpose simulation platforms to improve ease of operation and get greater insight into the performance of the protocols. A comparison between protocols that use single and multiple channels was done to study the increase in performance with added channels. Performance of these protocols for different reader speed was analyzed. Two anti-collision protocols Listen Before Talk (LBT) and Neighbor Friendly Reader Anti-collision protocol (NFRA) based on Carrier Sense Multiple Access with Collision Avoidance (CSMA-CA) and Time Division Multiple Access (TDMA) respectively are simulated using a Java based tool R2RIS. Simulation results showed that the LBT protocol gave approximately 4 times lesser waiting time when using 4 channels than the single channel NFRA protocol. Both protocols deliver similar performance at different reader speeds.

In this paper, we advocate implementing carrier sense multiple access with collision detection (CSMA/CD) in the broadband power line communication (BB-PLC) standard, G.hn, and show the gain in data rate obtained over carrier sense multiple access with collision avoidance (CSMA/CA). The use of CSMA/CD is made feasible due to the recent implementation of in-band full duplex operation in BB-PLC. We provide this implementation on a G.hn model using the NS-3 simulator, which we have made available as open-source. Our G.hn model implements physical and data link layers, including repeating function that makes it possible to simulate the long line network topologies (e.g., the network for electricity metering purpose). We also add IP/UDP layers to accomplish the higher layer protocol stack. We also provide analytical calculations of efficiency gains and validate them through our simulation results. We show that the highest achievable data rate with CSMA/CD is up to 5% higher than with CSMA/CA. Furthermore, we demonstrate that the protocol with CSMA/CD is less dependent on the number of active senders and has a smaller range of optimal contention window sizes (CW) for the same range of active senders, in comparison to CSMA/CA. This also simplifies the protocol implementation as the back-off algorithm for CSMA/CD does not vary CW as much as for CSMA/CA.

IEEE 802.15.4 employs a medium access control protocol based on carrier sense multiple access with collision avoidance (CSMA/CA). Channel sensing may have critical impact on the system throughput and energy consumption as well. In this paper, we investigate the effect of channel sensing on the CSMA/CA performance in IEEE 802.15.4 star-topology configured networks. We show that the hidden node ratio (i.e., the probability that any two child nodes cannot hear each other in a star-topology configured network) is highly associated with the target false-alarm probability of the channel sensing detector. We show that the CSMA/CA performance of IEEE 802.15.4 network can significantly be improved by adjusting the hidden node ratio.

The IEEE 802.15.3c/mmWave WPAN has been recently proposed as one of the most promising technologies that can allow broadband access in future 5G mobile networks. In this standard, the carrier sense multiple access with collision avoidance (CSMA/CA) technique was adopted to allow medium sharing between mobile devices co-located in the same small-cell. The performances of this access technique depend on two main parameters, the carrier sense threshold and the contention window derived from the persistence probability. One of the major limits of this method is that it can lead extensive contention and thus limited throughput. In this paper, we investigate the design of a contention based multiple access control technique for 5G wireless access networks where the carrier sense threshold and the persistence probability are dynamically adjusted according to the observed contention level observed by the device on the network. To this end, we model the multiple access paradigm in 5G networks using a non-cooperative game-theoretic framework, and we show that it admits an equilibrium. In addition, we propose a fully distributed multiple access control CSMA/CA based algorithm where the carrier sense threshold and the persistence probability are intelligently tuned according to the collision level gathered by the device on the shared wireless medium until reaching the equilibrium state. Through the simulations, we demonstrate that the proposed game theoretic based CSMA/CA outperforms the original version of the algorithm in terms of success transmission rate and delay.

In order to meet the requirement of dramatically growing mobile data, the operators improve their network by aggregating multiple carriers to increase the system capacity. Due to the limited availability of licensed spectrum, unlicensed spectrum with large amount of resources has attracted more and more world-wide interests recently. The Licensed Assisted Access (LAA) using LTE(-A) on unlicensed bands is investigated and being standardized in 3rd Generation Partner Project (3GPP) Release-13. This paper focuses on studying the co-existence techniques of multiple operators within LAA system. Although Listen-Before-Talk (LBT) mechanism is identified as a necessary feature in LAA to cope with the interference between Wi-Fi and LTE, it may not be efficient enough to mitigate the interference within LAA while between different operators. In this paper, we propose an enhanced LBT mechanism with cross-correlated information by utilizing assistant measurement report from users. System level simulation is conducted to illustrate the performance gain of the proposed method. It is shown that the enhanced LBT mechanism has outstanding performance in medium and high traffic scenarios in terms of user experienced throughput.