Novel LAA Waiting and Transmission Time Configuration Methods for Improved LTE-LAA/Wi-Fi Coexistence Over Unlicensed Bands
Authors : Moawiah Alhulayil & Miguel López-Benítez
Abstract : Long Term Evolution-Licensed Assisted Access (LTE-LAA) has been pointed out as a key solution to cope with the increasing amounts of data traffic and the scarcity of the licensed spectrum. The 3rd Generation Partnership Project (3GPP) has standardised LAA to operate over the 5 GHz unlicensed spectrum which is mainly occupied by Wi-Fi. It is a challenging problem to ensure a fair coexistence between these technologies. Several studies have been proposed in the literature to allow a fair LAA/Wi-Fi coexistence. In this work, various methods are proposed to adapt/select the waiting times for LAA based on the activity statistics of the existing Wi-Fi network. The main novelty is that the knowledge of the existing Wi-Fi activities is exploited to tune the boundaries of the Contention Window (CW) for LAA and to select fixed waiting times for LAA. Moreover, a dynamic method is proposed to adapt the Transmission Opportunity (TxOP) times for LAA based on the Hybrid Automatic Repeat Request (HARQ) feedbacks. The methods are evaluated using ns-3 network simulator based on the 3GPP fairness definition. We show that selecting fixed waiting times for LAA based on the existing Wi-Fi activities is more friendly to the existing Wi-Fi and provides better total aggregated throughputs for both coexisting networks compared to the 3GPP Category 4 Listen Before Talk (Cat 4 LBT) algorithm. Moreover, the proposed dynamic TxOP method is more friendly to the existing Wi-Fi and provides better total aggregated throughputs compared to the fixed TxOP period approach of the 3GPP Cat 4 LBT scheme.
Keywords : Licensed assisted access; LTE/Wi-Fi coexistence; ns-3, unlicensed spectrum; Wi-Fi
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LTE/Wi-Fi Coexistence in Unlicensed Bands Based on Dynamic Transmission Opportunity
Authors : Moawiah Alhulayil & Miguel López-Benítez
Abstract : With the rapid proliferation of smart devices, the demand for more licensed spectrum bands arises. Due to the scarcity of the licensed spectrum, the 3rd Generation Partnership (3GPP) has recently deployed Long Term Evolution (LTE) networks using the Licensed Assisted Access (LAA) scheme over unlicensed bands. On the other hand, the Wi-Fi technology is the main technology that operates over these unlicensed bands. Thus, the major concern is to attain a fair coexistence mechanism between these coexisting technologies (i.e., LTE and Wi-Fi). In this paper, we focus on the downlink scenario under different traffic loads to study the effect of the maximum Transmission Opportunity (TxOP) period for LTE-LAA in the performance of LTE-LAA/Wi-Fi coexistence. A dynamic TxOP period method is proposed to provide better fairness and higher total aggregated throughputs for the coexisting networks based on the Hybrid Automatic Repeat Request (HARQ) reports. The novelty of this work is that the existing HARQ reports are exploited to update the TxOP period for LAA in a dynamic manner. We show that the TxOP period plays a key role in the coexistence between LTELAA and Wi-Fi networks over unlicensed bands. The simulation results show that the proposed dynamic TxOP method improves the fairness and achieves higher total aggregated throughputs for both coexisting networks as compared to the static TxOP period used by the standard Category 4 LBT (Cat 4 LBT) method defined by 3GPP.
Keywords : Category 4 LBT; LTE-LAA/Wi-Fi coexistence; Licensed Assisted Access; Transmission Opportunity; Unlicensed spectrum.
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Methods for the Allocation of Almost Blank Subframes with Fixed Duty Cycle for Improved LTE-U/Wi-Fi Coexistence
Authors : Moawiah Alhulayil & Miguel López-Benítez
Abstract : In order to cope with the increased demand of wireless services and applications, LTE over unlicensed spectrum has been proposed to extend the operation of LTE to operate also over unlicensed bands. However, this extension faces various challenges regarding the coexistence between LTE-U and different technologies that use these unlicensed spectrum bands such as Wi-Fi technology. The first scenario of LTE allowing LTE to operate over unlicensed bands is LTE-Unlicensed duty cycling (LTE-U). Specifically, LTE-U can coexist with Wi-Fi by allowing LTE-U devices to transmit only in predetermined duty cycles (DCs) or to use adaptive DCs for LTE based on the activity measurements. In this paper, we investigate the downlink performance of LTE-U and Wi-Fi under different traffic loads. The main novelty of this work is to exploit the knowledge of the existing Wi-Fi traffic activity to select a fixed DC for LTE. Moreover, two proposed methods to allocate the blank subframes within LTE frames are provided. Simulation results using NS3 simulator for LTE-U and Wi-Fi coexistence mechanism under different traffic loads are provided. In particular, the results show that the coexistence mechanism between LTE-U and Wi-Fi in the 5 GHz band achieves better total aggregated throughputs for the coexisting technologies using the proposed approach. Moreover, the location of the blank subframes plays a key role in this coexistence in terms of the total aggregated throughputs.
Keywords : Almost blank subframe; Duty cycle; LTE/Wi-Fi coexistence; Unlicensed bands
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Static Contention Window Method for Improved LTE-LAA/Wi-Fi Coexistence in Unlicensed Bands
Authors : Moawiah Alhulayil & Miguel López-Benítez
Abstract : The 3rd Generation Partnership Project (3GPP) has recently defined a Licensed Assisted Access (LAA) scheme to enable Long Term Evolution (LTE) networks to use unlicensed frequency bands. However, the unlicensed bands are mainly occupied by the Wi-Fi technology. Hence, achieving fairness between LAA using LTE (LTE-LAA) and Wi-Fi in the unlicensed bands is a primary challenge. The 3GPP has recently standardised in Release 13 a Listen Before Talk (LBT) algorithm to ensure the fairness among these two technologies (LTE and Wi-Fi) over the unlicensed bands. In this paper, we focus on the downlink performance of LTE-LAA and Wi-Fi with different traffic loads. To achieve not only better fairness but also higher total aggregated throughputs for the coexisting networks, a static Contention Window (CW) selection method based on the fairness definition is proposed. The main novelty of this work is that the knowledge of Wi-Fi activity statistics is exploited effectively to select the CW of LAA. We show that the fairness between LAA and Wi-Fi networks depends on the LAA CW size adaptation criterion. Simulation results validate that the proposed method is effective in LAA/Wi-Fi coexistence scenario, can improve fairness performance and provide higher total aggregated throughputs for both coexisting networks compared with the current Category 4 LBT (Cat 4 LBT) algorithm defined in the 3GPP standard.
Keywords : Contention window; LAA/Wi-Fi coexistence, Licensed-Assisted Access; Listen-Before-Talk; Unlicensed bands
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Dynamic Contention Window Methods for Improved Coexistence Between LTE and Wi-Fi in Unlicensed Bands
Authors : Moawiah Alhulayil & Miguel López-Benítez
Abstract : Recently, the 3rd Generation Partnership Project (3GPP) announced standards that permit the Licensed-Assisted Access (LAA) of Long Term Evolution (LTE) to operate over unlicensed spectrum bands. This permission, which is a part of the 5G specifications, is due to the scarcity of the licensed spectrum and the increased use of wireless networks and services. However, these unlicensed bands are mainly occupied by 802.11 based WLAN devices. Thus, challenges arise for the efficient coexistence mechanism to share the same unlicensed band by LAA and Wi-Fi to maintain the quality of service and manage the interference among users. In this work, we propose new variable contention window (CW) methods for LAA to enable the coexistence of LTE and Wi-Fi in a fair manner based on the Wi-Fi statistics. The main novelty of this work is that the knowledge of Wi-Fi activity statistics is exploited to adapt the CW of LAA more effectively. These methods are evaluated based on the 3GPP fairness definition for such coexistence mechanisms under various traffic loads. We show that the fairness depends on the LAA CW size. Further, through simulation results, we show that the proposed schemes are more friendly to the existing Wi-Fi network, in particular for the higher traffic loads, compared with the existing Category 4 Listen-Before-Talk (Cat 4 LBT) algorithm defined in the 3GPP standard and provide higher total throughputs for both coexisting networks, improving the overall network performance.
Keywords : Coexistence mechanism; Contention window; Licensed-Assisted Access; Listen-Before-Talk
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Coexistence Mechanisms for LTE and Wi-Fi Networks over Unlicensed Frequency Bands
Authors : Moawiah Alhulayil & Miguel López-Benítez
Abstract : Recently, mobile data traffic has rapidly grown which results in many challenges especially in the radio spectrum needs. Thus, operating Long Term Evolution (LTE) in unlicensed bands is becoming an attractive area of research. In particular, the idea is to utilise the unlicensed spectrum by deploying other technologies over these unlicensed bands to coexist with Wi-Fi, radar, and Bluetooth. On the other hand, this coexistence between LTE and Wi-Fi technologies faces many limitations and challenges over these bands. In this context, this paper presents a coexistence analysis between LTE and Wi-Fi over the unlicensed 5 GHz band. The coexistence mechanism is studied by deploying different scenarios of LTE. The first scenario is by using LTE-Unlicensed duty-cycling (LTE-U), while the second one is by using LTE Licensed-Assisted Access (LTE-LAA). In particular, simulation results using NS-3 simulator for the throughput and latency for different coexistence deployments are provided. The simulation results show that the coexistence mechanism between LTE-LAA and Wi-Fi in the 5 GHz band outperforms that of LTE-U with Wi-Fi. Furthermore, the results show that the design of the Listen Before Talk (LBT) algorithm in LTE-LAA plays an important role in the coexistence mechanism. On the other hand, the impact of changing some parameters on LTE and Wi-Fi performances are studied. In particular, the results show that the performance is not affected by changing many parameters of LTE and Wi-Fi and LBT algorithm needs some modifications to deploy a fair coexistence mechanism.
Keywords : stence mechanism; duty-cycling; Licensed-Assisted Access; radio spectrum; 5 GHz band
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Performance analysis of amplify-and-forward cognitive relay networks with interference power constraints over Nakagami-m fading channels
Authors : Mohammad M. Shurman, Mamoun F. Al-Mistarihi & Moawiah M. Alhulayil
Abstract : With the wide-spread wireless applications and services, the spectrum scarcity has become a challenging problem. Thus, it is necessary to find a solution to have more spectrum bands. One from these solutions is the cognitive relay network, where we can increase the spectrum utilization by combining the cognitive radio (CR) with cooperative spectrum sharing systems. In this paper, the performance of cognitive relay networks under interference power constraints from the primary user (PU) is studied. Here, the system models are studied by utilizing different scenarios. The first scenario is by using a single amplify-and-forward (AF) relay, and the second one is by using a single AF relay with selection diversity. Tabulated expressions for the outage probability (OP) are derived over independent and non-identically distributed Nakagami-m fading channels. Numerical results show that the cooperative spectrum sharing transmission with a single AF relay and selection diversity outperforms both the direct transmission and the transmission using a single AF relay for the underlay cognitive relay networks. Furthermore, the results show that the outage performance depends on the minimum fading severity parameters of the two hops of the secondary user (SU) and the OP decreases as the PU moves away from the SU network.
Keywords :
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Outage Probability of Amplify-and-Forward Underlay Cognitive Relay Networks with Selection Diversity over Nakagami-m Fading Channels
Authors : Moawiah Alhulayil, Mamoun F. AI-Mistarihi & Mohammad Shurman
Abstract : In this paper, the outage performance is investigated for cognitive dual-hop relay networks with amplify-and-forward (AF) relay and selection combining (SC) receiver at the destination under spectrum sharing constraints on primary user (PU) over independent and identically distributed (i.i.d.) Nakagami-m fading channels. We derive an exact closed-form expression for the outage probability (OP) of the considered system under the peak interference power Ip at the primary user, and the impact of the PU location on the OP performance is studied also. Moreover; the effects fading severity for the two hops on the OP is investigated also for this cognitive relay network (CRN).
Keywords : Nakagami-m fading, cognitive relay network, dual hop, cognitive radio, amplify-and-forward relaying, selection diversity, outage probability
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Outage Probability of Dual-Hop Amplify-and-Forward Cognitive Relay Networks Under Interference Power Constraints Over Nakagami-m Fading Channels
Authors : Mohammad M. Shurman, Mamoun F. Al-Mistarihi & Moawiah M. Alhulayil
Abstract : In this paper, the performance of the outage probability (OP) for cognitive dual-hop relay networks with amplify-and-forward (AF) relay under spectrum sharing constraints on primary user (PU) over independent and identically distributed (i.i.d.) Nakagami-m fading channels is investigated. An exact closed-form expression for the OP of the proposed system is derived under the peak interference power (Ip) at the primary user. The impact of the PU location on the OP performance is studied also.
Keywords : Nakagami-m fading, cognitive relay network, dual hop, cognitive radio, amplify-and-forward relaying, outage probability
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Closed-form Expression of Bit Error Rate in Dual-Hop Dual-Branch Mixed Relaying Cooperative Networks with Best-Path Selection over Rayleigh Fading Channels
Authors : Moawiah Alhulayil, Ali M Hayajneh, Mamoun F Al-Mistarihi, Mohammad Shurman & Khalid A Darabkh
Abstract : In this paper, a new cooperative-diversity network with simple dual hop virtual diversity with mixed decode-and-forward and amplify-and-forward with best path selection is proposed. A closed-form expression for the average bit error rate of the communication system, assuming phase shift keying modulation scheme over independent non-identical Rayleigh fading channels, is derived. The results show that the proposed model outperforms the regular cooperative network models with a sub-optimal allocation for the relay relative distance.
Keywords : Rayleigh fading, best path selection, dual hop, dual branch, maximal ratio combining, error performance, outage probability
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