Hard Handoff Research Articles

Application of adaptive guard channel reservation under hard handoff constraint in wireless cellular network

Application of adaptive guard channel reservation under hard handoff constraint in wireless cellular network

Performance Analysis of Multimedia Communications Hard Handoff over Fading Channel (Dept.E)

Handoff is an essential element of cellular communication systems. Efficient handoff algorithms can be considered as a cost-effective way of enhancing the capacity and the quality of service (QoS) of cellular systems. In this paper, the performance of no priority schemes and first- in- first -out (FIFO) handoff queuing schemes are considered. The performance of signal power multimedia communications (SPMC) is studied for multimedia communications queuing over a shadow and ricean fading channel. Computer simulations are performed to calculate the probability of new call blocking (Pb) and probability of handoff dropping (Pd) using different types of handoff strategies. Results indicate that the developed scheme reduce the probability of multimedia handoff call dropping as compared to no priority schemes with 18% in case of no fading, while it provides about 8% - 18% improvement in case of shadow fading channel, and it provides about 4% -14% improvement in case of ricean fading channel.

Coverage Analysis and Optimization for High-Speed Railway Communication Systems With Narrow-Strip-Shaped Cells

As is known, the cell coverage analysis of the high-speed railway (HSR) communication system is quite different from that of the public land cellular communication system. This paper investigates the cell coverage for the HSR communication system with narrow-strip-shaped cells. By utilizing the hard handoff scheme, a closed-form expression for the edge coverage probability (ECP) is first derived. Then, a theoretical expression for the percentage of the cell coverage area (CCA) is obtained, which is derived as the summation of the ECP, and a positive increment. To improve coverage performance, a coverage optimization problem is formulated to minimize the required number of base stations (BSs) under the coverage constraint, and the total coverage distance constraint, and then an optimal BS deployment scheme is proposed to solve the optimization problem. Numerical results indicate that all theoretical results match well with the simulation results, which verifies the correctness of the theoretical analysis. Moreover, the impacts of the received power threshold, cell radius, handoff hysteresis, transmit power, shadow fading, and path loss exponent on the cell coverage performance are also provided. Furthermore, compared to the existing coverage scheme, the proposed BS deployment scheme can improve the coverage performance significantly.

MRPL+: A mobility management framework in RPL/6LoWPAN

The next generation Internet (also known as Internet-of-Things – IoT), will ubiquitously integrate trillions of computing devices of all kinds, shapes and sizes. For this ubiquity to materialize, a key aspect will certainly be interoperability, the capability of different technologies (e.g. different communication protocols at both horizontal and vertical levels, different hardware platforms, different operating systems, fixed and mobile nodes, etc) to talk to and understand each other. A major enabler for this interoperability is the use of standard and commercial-off-the-shelf technologies (e.g. communication protocols, hardware platforms, operating systems). As IPv6 has become the de-facto communication technology for the Internet, 6LoWPAN has recently started paving the way for extending the Internet to low-power low-cost wireless devices. However, while mobility support will be a requirement (or at least beneficial) in many applications contexts, the support of mobile nodes in the default 6loWPAN/RPL protocol leads to excessive packet loss and delays.In this work, we show that interoperability between fixed and mobile nodes can be successfully achieved through the use of appropriate hand-off and topology management techniques. We propose a mobility management framework (dubbed mRPL+) unifying two hand-off models: (1) hard hand-off, where a mobile node has to break a link before finding a new link, and (2) soft hand-off, where a mobile node selects the new link before disconnecting from the current one. Importantly, mRPL+ is integrated in the 6LoWPAN/RPL stack in a backward compatible manner. Simulation results indicate that in a network with mobile nodes, packet delivery ratio with mRPL+ is nearly 100%, where RPL achieves 80% in best-case. Hand-off process has a disconnected period of few milliseconds (hand-off delay = 4 ms), while RPL experiences few seconds of disconnection during node’s mobility (3−10 s).

Performance Analysis of TCP and its Enhancement for Quality of Service in Mobile Wireless Networks in Single Traffic Using Prioritised Hard Handoff (PH2)

The research activities in mobile computing and wireless networks strongly indicates that mobile computers and their wireless communication links will be an integral part of the current internet works. Communication over wireless links is characterised by limited bandwidth, high latency, high bit-error rates and temporary disconnections. Most often, networks with wireless links and mobile hosts incur significant losses due to handoff. It is also most important that in wireless environment TCP (transmission control protocol) causes degraded end-to-end performance. In this paper, we tried to give solutions to these problems. We adopt a new method to improve the end-to-end reliable transport performance in mobile wireless environment by incorporating changes to network-layer at the base station and mobile host and preserve end-to-end semantics of TCP. The methodology employs NDG (normalised delay gradient) loss-predictor function to determine congestion losses from that of transmission loss. The sender window can adjust its size depending on the loss information. If the loss is due to congestion, congestion control algorithm is invoked to decrease the flow rate. If the loss is due to handoff (transmission loss), immediate-recovery algorithm is invoked to recover the losses caused by the sender TCP. Stochastic equations are used to analyse, i) arrival rate handoff calls, ii) blocking probability of handoff request, iii) distinguish packet loss due to congestion or handoff, iv) dynamics of sender window, v) queue length at the ingress point of the BS router , vi) throughput, and vii) the losses due to congestion and handoff blocking. Our results provide better way understanding the problem of calls drop due to handoff, and providing most accurate solutions for mobile wireless system.

Joint Routing and Admission Control in Wireless Mesh Network

Wireless Mesh Network is a promising technology with many challenges yet to be addressed. Novel and efficient algorithms need to be developed for routing and admission control with the objective to increase the acceptance ratio of new calls without affecting the Quality of Service (QoS) of the existing calls and to maintain the QoS level provided for the mobile calls. In this paper, a novel Markov Decision-based Admission Control and Routing (MDACR) algorithm is proposed. The MDACR algorithm finds a near optimal solution using the value iteration method. To increase the admission rate for both types of calls, a multi-homing admission and routing algorithm for handoff and new calls is proposed. This algorithm associates the user with two different access points which is beneficial in a highly congested network and proposes a new routing metric to assure seamless handoff in the network. Our proposed algorithm outperforms other algorithms in the literature in terms of handoff delay, blocking probability, and number of hard handoff.

Smart Downlink Scheduling for Multimedia Streaming Over LTE Networks With Hard Handoff

This paper presents a novel smart downlink scheduling scheme to enhance the performance of multimedia transmission over long-term evolution (LTE) networks. LTE represents a promising framework for the next-generation broadband multimedia services because of its significantly increased data rate over 3G cellular networks. However, the current LTE scheduling scheme has largely been designed for general data traffic without adequate consideration of multimedia characteristics. Moreover, the hard handoff (HO) procedure adopted in LTE will further degrade the multimedia services when the mobile user moves from one cell to another. Even with increased data rate, current LTE systems still cannot deliver the expected quality of service (QoS) to the mobile users under various mobility scenarios, especially when the hard HO is evoked. Aiming at overcoming these major challenges, we develop in this paper a QoS-driven smart downlink scheduling scheme for enhanced multimedia transmission over LTE networks. The proposed design shall take the following QoS metrics into consideration: 1) the delay constraint of voice-over-Internet protocol flow; 2) the packet deadline of video flow; and 3) the service degradation induced by the hard HO procedure. We achieve the design objectives by creating three QoS-driven operational control modules: 1) a transmission delay control module to ensure the on-time arrival of various types of multimedia data; 2) an HO control module to warrant continuous multimedia services when the user moves across a cell boundary; and 3) a resource allocation module to strategically map the requested flows to best fit radio resource blocks. The simulation results confirm the performance gain of the proposed scheme.

A New Seamless Handover Mechanism for IEEE 802.16e in WiMAX Networks

sublayers accepts higher-layer protocol data units (PDUs) from ATM cell-based or packet-based network layers. The Common Part Sublayer (CPS) provides the core MAC functionality of system access, bandwidth allocation, connection establishment, and connection maintenance. The Security Sublayer provides authentication, secure key exchange, and encryption. The IEEE 802.16e (3) system is based on OFDMA physical structure, mobile subscriber stations (MSS) basically conduct three handoff methods: Hard Handoff (HHO), Fast Base Station Switching (FBSS) and Macro Diversity Handover (MDHO). The first method (HHO) is a mandatory while the other two methods are optional. In HHO, the Mobile Subscriber (MS) is connected to only one Base Station (BS) at any given time. If the MS decides to handover from the serving BS, it selects only one target BS from a subset of recommended BSs and starts connecting to it before disconnecting from the current serving BS. An important objective when designing a handover mechanism is to minimize the time spent in the handover transition to ensure that the MS does not experience service interruption during the handover.

Performance analysis of mobile wimax handoff using qualnet simulator

Mobile WiMAX is a wireless technology based on IEEE802.16e for broadband wireless access. Mobile WiMAX introduces the most significant new feature, mobility to support for handovers, which can be considered as a basic requirement for mobile communication system. The mandatory handoff method is hard handoff for mobile WiMAX and other two optional soft handoff methods are macro diversity handoff and fast base station switching handoff method. Hand over delay generates during data transmission but handover delay should be less than 50ms over real time applications such as Voice Over Internet Protocol (VOIP). The existing draft standard considers only the received signal strength when deciding handover. The mobility improvement handover scheme that depends upon the velocity factor has been taken into consideration in this paper. The proposed scenario has been implemented using QualNet network simulator which has led to less handover time.

Modeling Prioritized Hard Handoff Management Scheme for Wireless Mobile Networks

The channel associated with the current connection serviced by a base station is changed while a call is in progress. Usually, continuous service is achieved by supporting handoff from one cell to another. It is often initiated either by crossing a cell boundary or by deterioration in quality of the signal in the current channel. The existing call is then changed to a new base station . For the traffics which are non stationary at and are away from the servicing base station , the chances of a call to be handed off are increasing. In this paper we propose a scheme S MH 2 to modeling and implementing a traffic el mod with handoff behavior for wireless mobile networks . The simulation model S MH 2 with priority is developed to investigate the performance behavior of hard handoff strategy. Novelty of the proposed model S MH 2 results that it can improve call blocking rate of handoff calls . In addition to this, measurement of blocking probabilities for both g originatin calls and handoff calls is another impressive achievement of the model. Index Terms — Mobile station, traffic model, arrival rate, departure rate, blocking probability, call blocking rate

A proposal for proxy-based mobility in WSNs

Inability to meet the key requirement of efficient mobility support is becoming a major impairment of wireless sensor network (WSN). Many critical WSN applications need not only reliability, but also the ability to adequately cope with the movement of nodes between different sub-networks. Despite the work of IETF’s 6lowPAN WG and work on the use of MIPv6 (and many of its variants) in WSNs, no practical mobility support solution exists for this type of networks. In this paper we start by assessing the use of MIPv6 in WSNs, considering soft and hard handoff, showing that, although feasible in small networks, MIPv6 complexity leads to long handoff time and high energy consumption. In order to solve these problems, we propose a proxy-based mobility approach which, by relieving resource-constrained sensor nodes from heavy mobility management tasks, drastically reduces time and energy expenditure during handoff. The evaluation of both MIPv6 and the proposed solution is done by implementation and simulation, with a varying number of nodes, sinks and mobility strategies.

A Soft Computing Based Adaptive Call Admission Control Scheme for Bi-Class Traffic in CDMA Cellular Network

Soft handoff in CDMA cellular system increases system capacity as compared to hard handoff as interference is reduced by transmitting signals as lower power level. A CDMA cellular system involving voice and data calls is considered in this paper. The model proposed in this paper is for data and voice services (Bi-class). It is based on reservation for handoff voice and data calls along with call queuing scheme for handoff data calls. Preemptive priority scheme is used for handoff voice calls over ongoing data calls. Upper channel limits are set for new voice as well as data calls to give priority to handoff calls. For better resource management and efficient call admission to originating and handoff calls, Neuro-fuzzy call admission controller is designed. This controller uses the adaptable feature of soft handoff threshold parameters to accommodate important voice and data calls. The proposed ASNFC controller is compared with the two variants of Bi-class CAC scheme. General Terms Call Admission Control, Soft Computing

A Mobility Improvement Handover Scheme for Mobile-WiMAX

This paper presents a mobility improvement handover algorithm with less scan time implementation for Mobile WiMAX. Mobile WiMAX is a wireless technology based on IEEE802.16e for broadband wireless access. Mobile WiMAX introduces the most significant new feature, mobility to support for handovers, which can be considered as a basic requirement for mobile communication system. The mandatory handoff method is Hard Handoff for Mobile WiMAX and other two optional soft handoff methods are Macro Diversity Handoff and Fast Base Station Switching Handoff method. Handover delay generates during data transmission but handover delay should be less than 50milli second for real time applications such as VoIP. The existing draft standard considers only the received signal strength (RSS) when deciding handover. The mobility improvement handover scheme that depends upon the velocity factor has been taken into consideration in this paper. The proposed scheme skips some unnecessary handover stages, reduces handover delay by adjusting the handover parameters viz. handover RSS trigger and threshold handover RSS trigger value to improve the velocity of the mobile station. The proposed scenario has been implemented using QualNet network simulator which has lead to less handover time.

Allocation of power for Universal Mobile Telecommunication Services network during Soft Handoff

In order to provide a multiple services, especially multimedia and high-bit-rate packet data, Universal Mobile Telecommunication Services adopted Wideband Code Division Multiple Access (WCDMA) act as the mainstream air interface solution for the third-generation networks. An in-depth study of Soft Handoff (SHO) in the downlink direction of WCDMA network is carried out. The link-level study begins with the SHO effects on the downlink interference analysis and power allocation for each downlink-dedicated channel. To the users at the cell boundaries, the inter-cell interference is the main part of the total interference, especially with higher orthogonality. Simulation result shows that SHO decreases the probability of over-power Quality of Service (QoS) deterioration for the users at cell boundaries. However, 2-way SHO has a better performance than hard handoff and 3-way SHO, because it requires less dedicated power to meet the QoS for corner users.

The Complementary Use of 3G WCDMA and GSM/GPRS Cellular Radio Networks

The traffic performance of integrated 3G wide-band code division multiple access (WCDMA) and GSM/GPRS network is evaluated. This type of network links two cellular radio systems which have different set of frequency bands and the same coverage size. The base station of 3G WCDMA is installed on an existing GSM/GPRS site. Dual-mode mobile terminals use handoff to establish calls on the better system. The soft handoff or inter-frequency hard handoff occurs when mobile terminals of 3G WCDMA or GSM/GPRS move between two adjacent cells, respectively. The inter-system hard handoffs are used between 3G WCDMA and GSM/GPRS systems. The data rate conversions between different systems, soft handoff region size, multiple data rate multimedia services, and the effect of the mobile terminal mobility on the user mean dwell time in each system are considered in the study. The simulation results demonstrate that a great traffic performance improvement on the complementary use of 3G WCDMA and GSM/GPRS cellular radio networks compared with the use of GSM/GPRS cellular radio networks. When high-data rate transmission is chosen for low-mobility subscribers, both the handoff failure probability, and carried traffic rates increase with the new call generation rate. However, both rates decrease conversely with the increasing new call generation rate as soon as the new call generation rate exceeds a critical value. This causes the integrated networks saturation. The higher mean speed for the mobile terminals produces lower new call blocking probabilities and total carried traffic. The new call blocking probabilities and total carried traffic increase with the size of the soft handoff region.

Adaptive semi-soft handoff for Cellular IP networks

Various advances in technologies have led to a myriad of wireless mobile devices to ubiquitously connect to the internet. This creates a significant demand for seamless wireless network connectivity. The Cellular IP semi-soft handoff protocol has been proposed to satisfy this demand. Studies have shown that it performs better than the conventional hard handoff protocol. However, these studies are based on unrealistic assumptions of symmetrical network topologies and fixed loads. In practice, network topology can be asymmetric and network load fluctuates. Semi-soft handoff uses fixed handoff parameters for stream synchronization and mobile host's tune-in time, which may work well for the symmetrical network setups, but performs poorly with unbalanced and dynamically changing networks. This paper proposes adaptive semi-soft handoff protocol (Adaptive-SS) to address this issue by dynamically changing handoff parameters based on network conditions during handoff. Our simulation study shows that Adaptive-SS significantly reduces network traffic and packet losses/duplications during handoff, while still minimising handoff latency.

An Adaptive Hard Handoff Algorithm for Mobile Cellular Communication Systems

In this letter, we propose an adaptive hard handoff algorithm with a dynamic hysteresis value based on the received signal strength from the serving base station, for mobile cellular communication systems. A discrete-time method is presented to evaluate handoff algorithms analytically. Performance is evaluated in terms of the average number of handoffs, the probability of link degradation, and the average handoff delay. Numerical results and simulations demonstrate that the proposed algorithm outperforms the handoff algorithm with fixed hysteresis values and the handoff algorithm using both threshold and hysteresis.

MCIP: A 3G/IP Interworking System Supporting Inter-Cluster Soft Handoff

In this paper, a novel 3-tier Mobile Cellular IP (MCIP) access network is proposed for interworking between a third generation (3G) wireless cellular system and a wireline Internet Protocol (IP) based network. An inter-cluster hard handoff scheme and an inter-cluster soft handoff scheme are proposed, based on the 3-tier MCIP system model, the core network protocol stacks, and the underlying MCIP routing algorithm. The core network protocol stack is presented to integrate the 3G radio interface and the IP-based core network, and to provide the access network with capability to support soft handoff macroscopic space diversity. The MCIP hard and soft handoff schemes are compared with the hard handoff schemes used in the Cellular IP and HAWAII access networks. The MCIP access network is more efficient in terms of signaling cost, but has the same scalability as Cellular IP and HAWAII. Both MCIP hard and soft handoff schemes enable IP packets to be delivered within the MCIP access network in-order without loss and duplication, a highly desired attribute for real-time multimedia applications. The advantages of supporting soft handoffs and quality-of-service (QoS) provisioning for real-time services are achieved at slightly increased system complexity.

Connectivity, performance, and resiliency of IP-based CDMA radio access networks

IP-based radio access networks (RAN) are expected to be the next generation access networks in UMTS and CDMA networks. The question of connectivity, i.e., how best to connect base stations to the radio network controllers (RNC) in an IP-based RAN, has not been addressed by researchers. Furthermore, given a connection configuration, an RNC selection algorithm that assigns an incoming call to an RNC is also necessary. This paper examines RAN connectivity and its impact on the performance and resiliency of the wireless network using different RNC selection algorithms. For homogeneous networks, we show that the proposed min-load-1 algorithm, which allows at most one hard handoff in order to accommodate each incoming call request, delivers performance close to the optimal algorithm. We also show that allowing a few base stations to connect to two RNCs (a 10 percent increase in the number of links in our network) results in resiliency to RNC failures that is comparable to the resiliency of RANs with full-mesh connectivity. Finally, for heterogeneous networks, we show that the min-load-k algorithm (with at most k hard handoffs per call) is effective in handling load imbalances. These results provide strong motivation for deploying IP-based RAN, as they suggest that enhancing current point-to-point RAN with few additional links and allowing a few hard handoffs to accommodate incoming calls can result in significant gains in performance and resiliency

Cellular CDMA capacity with out-of-band multihop relaying

In this paper, we consider the capacity of cellular code division multiple access (CDMA) when there is out-of-band ad hoc traffic relaying. The mobile stations (MSs) are dual-mode, having both ad hoc and cellular CDMA radios. An active MS is free to choose any available relay station (RS) within its ad hoc radio coverage area for dual-hop communication with the CDMA base station (BS). Communications between the RSs and the MSs use bandwidth which is available to the ad hoc radio and does not consume the CDMA capacity. Using this mechanism, CDIVIA interference can be reduced by dynamically selecting RSs which have more favorable CDMA link characteristics. Several relay station selection criteria are considered, namely, ad hoc relaying with low relative interference (ARRI), with best link gain (ARLG), and with shortest distance (ARSD). The relay station selection protocols are compatible with existing wireless local area network (WLAN) standards such as IEEE 802.11. An analytic model is used to compute the effects on uplink and downlink CDMA capacities when out-of-band relaying is added. The results show that very significant capacity improvements are possible by using these criteria compared with conventional CDMA with hard or soft handoff. Ad hoc relaying which dynamically tracks CDMA link quality can achieve greater capacity improvements than that using a distance-based relay station selection. Relaying, which considers both signal and interference conditions, achieves better capacity than that based on signal link quality alone.