Mobility management with the central-based location area policy

In Long Term Evolution (LTE) system the Tracking Area (TA) is a group of cells in which User Equipment (UE) may move freely without performing location update process. The TA scheme has many limitations such as ping-pong effect and massive mobility signaling congestion. To overcome the limitations of the TA scheme, Tracking Area List (TAL) scheme is introduced. TAL is a group of TAs and if a UE is registered to one TAL it will not perform TAL update. In LTE system mobility management techniques are used to keep track of the current location of the UE which are location update and paging techniques. These techniques induce system overhead in both system signals and bandwidth consumption. In this paper we will examine the effect of TAL design in reducing this signaling overhead, taking into account TAL overlapping which mean that a cell may be included in more than one TAL. For a given TA and TAL design the overall signaling overhead was calculated. Results obtained showed that the TAL scheme gives minimum signaling overhead when compared with the TA scheme.

On dynamic signaling congestion mitigation by overlapping tracking area lists

We consider the allocation of spectral and power resources every subframe (1~ms) on the uplink of the Long Term Evolution (LTE) wideband orthogonal frequency division multiple access (OFDMA) cellular network. System bandwidth is divided into multiple sub-bands. The fractional power control to manage interference is allowed to be a function of the sub-band. Moreover, the channel gains from the base-station to the mobiles (user equipment (UE) in LTE) can vary with the sub-band. The power and spectral resources are to be allocated among different UEs in a cell based on channel conditions, desired fairness/QoS, and constraints on power due to interference and power limitation at a UE. For $N$ UEs and $M$ sub-bands, we exploit the structure of the underlying optimization problem to obtain an $O(NM)$ algorithm for optimal resource allocation when a UE can be allocated resources in a non-contiguous manner in frequency. To implement this in an OFDMA system, we delineate a simple control signalling structure where the UE computes in $O(M)$ time a waterfilling solution every subframe it is assigned resources. When the allocation is restricted to contiguous allocation in frequency due to single carrier constraint in LTE, we convert the solution computed above in $O(NM)$ time into a feasible solution. For typical network scenarios, the solution thus computed is numerically shown to be very close to the optimal solution with no restrictions.

Handover (HO) algorithms, managed by Mobility Management Entity (MM), and Scheduling algorithms, managed by Radio Resource Management Entity (RRM) are both the most important aspects in the next-generation cellular systems 3GPP Long Term Evolution (LTE). When a User Equipment (UE) is in motion, the constraints of offering better Quality of Service (QoS), especially in Real Time applications, increase. This is why the design of a powerful handover algorithm is essential, in order to ensure a seamless transfer of a UE to a new cell. In this article, we propose a new HO algorithm based on the Available Bandwidth prediction at the eNBs level. The improvements proposed by our scheme compared to other HO algorithms such as LTE Hard Handover Algorithm (LHHA), Integrator Handover and LTE Hard Handover Algorithm with Average RSRP Constraint (LHHAARC) has been shown via different parameters namely throughput, system delay and Packet Loss Ratio (PLR). Using LTE-Sim simulator, all HO algorithms were simulated against the three well-known scheduling schemes, namely, Proportional Fair (PF), Exponential Proportional Fairness (EXP / PF) and Modified Largest Weighted Delay First (MLWDF). The objective is to define a synthesis allowing the automatic choice of the proper scheduling scheme to use, according to the HO decision algorithm predefined by the system.

In Long Term Evolution (LTE), service area is divided into tracking areas (TAs), which consist of a group of cells and do not overlap with each other, and a TA list (TAL) is assigned to a mobile station (MS). Thus, location of an MS is managed by a granularity of a TAL and an MS does not need to register its location when it moves within TAs of the assigned TAL. In this paper, it is assumed that each TA consists of only one cell and TAL is formed by a group of cells. As a preliminary work to the optimal design of TAL for an individual MS, we validate the usefulness of the proposition that a TA consists of only one cell and TAL can be adaptively designed for each MS, by assuming uniform mobility model of MSs to simplify the analysis. TAL for an MS is designed as rings of cells (TAs) from the last update cell (TA), as an example of optimal design of TAL, by applying the concept of movement-based location registration. An optimal movement threshold for the TAL is derived periodically, using measured traffic and mobility characteristics of an MS during the time interval between two consecutive session arrivals. Finally, a new TAL is adaptively designed for an MS, based on the newly derived optimal movement threshold.

When a mobile operator migrates its network from the third generation (3G) system to Long Term Evolution (LTE), both 3G and LTE will coexist for a period of time. Since the 3G circuit-switched (CS) voice mechanism is more mature and available than that for the LTE Voice over Internet Protocol (VoIP), the operator may consider CS fallback (CSFB) as a solution for providing reliable voice calls. According to the 3G Partnership Project (3GPP) CSFB procedure, when a mobile user in the LTE network has an incoming or an outgoing call, the user equipment (UE) falls back from LTE to Universal Mobile Telecommunications System (UMTS). When the call is complete and released, the UE immediately returns to LTE. If the next activity for the UE is another voice call, immediately switching from UMTS to LTE may not be efficient. In this case, the UE has to perform another CSFB. To resolve this issue, we suggest delaying the returns to avoid unnecessary CSFBs, which is called delayed return (DR). Based on the measurements from the real UMTS and LTE networks, we develop an analytic model for investigating the performance of the CSFB with DR. This paper indicates that the DR scheme can effectively reduce the CSFB costs by up to 60%.

Network slicing has been viewed as one of the key architectural technologies for the next generation (5G) mobile network. The mobility pattern of User Equipments (UEs) in different network slices poses great challenge to the mobility management for the 5G systems, which is different from that for the 4G systems. In this paper we propose a multiple level tracking area (TA) and tracking area list (TAL) structure which considers the characteristics of UE mobility pattern and UE density of slices to analyze the location update frequency and the paging frequency of UE. Based on this structure, we employ an embedded Markov chain model to find a theoretically optimal TAL configuration for slice UEs by leveraging sequential and parallel paging schemes respectively. Numerical results demonstrate the effectiveness of our proposed analytical model and verify that the proposed multiple level TA architecture can significantly reduce the total signaling overhead in comparison with the legacy single level TA strategy.

Heterogeneous networks (HetNets) are expected to be a key feature of long-term evolution (LTE)-advanced networks and beyond and are essential for providing ubiquitous broadband user throughput. However, due to different coverage ranges of base stations (BSs) in HetNets, the handover performance of a user equipment (UE) may be significantly degraded, especially in scenarios where high-velocity UE traverse through small cells. In this article, we propose a context-aware mobility management (MM) procedure for small cell networks, which uses reinforcement learning techniques and inter-cell coordination for improving the handover and throughput performance of UE. In particular, the BSs jointly learn their long-term traffic loads and optimal cell range expansion and schedule their UE based on their velocities and historical data rates that are exchanged among the tiers. The proposed approach is shown not only to outperform the classical MM in terms of throughput but also to enable better fairness. Using the proposed learning-based MM approaches, the UE throughput is shown to improve by 80% on the average, while the handover failure probability is shown to reduce up to a factor of three.

Differentiated quality-of-Service (QoS) techniques are widely used to distinguish between different service classes and prioritize service needs in mobile networks. Mobile Network Operators (MNOs) utilize QoS techniques to develop strategies that are supported by the mobile network infrastructure. However, QoS deployment strategy can ensure that the radio resources provided by the base station are easily consumed if it is not used correctly or when different techniques are used all together. In this paper, we propose a scheduling algorithm and compare two different QoS deployment strategies for prioritized User Equipment (UEs) (with higher scheduling rates and dedicated bandwidth) that MNOs can use in the current infrastructure, using a commercial real-time Long Term Evolution (LTE) network in different test scenarios. Moreover, we expose the real-time user experience in terms of uplink throughput and analyze results of the UE’s real-time key performance indicators (KPIs) in detail. Experiment results are evaluated considering the implications of different QoS support types on network coverage and capacity planning optimizations. Our results demonstrate that even though pre-configured resource allocations can be given to prioritize UEs, the experience of all the UEs can be affected unexpectedly in the presence of many UEs who have received different QoS deployment support. Our experimental observations have revealed that location of the UEs with respect to Base Station (BS) and the availability of dedicated bandwidth UEs inside cell may have implications on the apriori defined resource allocation strategies of the other UEs.

Due to the power consumption issue of user equipment (UE), Single-Carrier FDMA (SC-FDMA) has been selected as the uplink multiple access scheme of 3GPP Long Term Evolution (LTE). Similar to OFDMA downlink, SC-FDMA enables multiple UEs to be served simultaneously in uplink as well. However, the single carrier characteristic requires that all the allocated subcarriers to a UE must be contiguous in frequency with each time slot. Moreover, a UE should adopt the same modulation and coding scheme at all allocated subcarriers. These two constraints do limit the scheduling flexibility. In this paper, we formulate the UL scheduling problem with proportional fairness support by taking two constraints into consideration. Since this optimization had been proven to be an NP-hard problem, we further develop one heuristic algorithm. We demonstrate that competitive performance can be achieved in terms of system throughput, which is evaluated by using 3GPP LTE system model simulations.

This paper presents the link-level performance of downlink non-orthogonal multiple access (NOMA) with successive interference cancellation (SIC) receiver, considering the influence of error vector magnitude (EVM). In our evaluations, for the case of a 1-by-2 transmission and the number of NOMA multiplexed users is two, we clarify the performance of NOMA for cell-center user equipment (UE) with codeword level SIC (CWIC) receiver and the performance of the cell-edge UE, which does not apply SIC. Based on link-level performance evaluations, we show that the performance of CWIC receiver is almost the same as that of ideal SIC when the allocated transmit power ratio to cell-center UE is less than 0.35, the modulation and coding scheme (MCS) of cell-center UE is 16QAM (R = 0.51) or 64QAM (R = 0.47), and the MCS of cell-edge UE is QPSK (R = 0.51). Furthermore, we also show that, when EVM value is 4 % and the allocated power ratio to cell-center UE is between 0.2 and 0.37, the level of degradation due to the influence of EVM is below 0.6 dB, which is almost the same level of degradation as that of orthogonal frequency division multiple access (OFDMA) for the EVM value required by 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE). On the other hand, we show that the influence of EVM is marginal for cell-edge UE compared to cell-center UE. However, when the cell-center UE uses a higher order modulation such as 64QAM, we show that the required SNR of cell-edge UE increases due to the increase in inter-user interference. Based on these results, we clarify that it is important for the base station (BS) to take into account the target BLER and influence of EVM when selecting the MCS and allocated transmit power ratio of NOMA UEs.

The purpose of the paper is to examine if public long term evolution (LTE) network is suitable for smart grid (SG) automatic metering usage, in a suburban scenario, without causing significant hindrance to typical LTE traffic. In addition, the same generalized suburban scenario is evaluated with a hybrid sensor - LTE network where wireless sensor network (WSN) cluster heads are also equipped with LTE remote terminal units (RTUs). The simulation topology is formed as a suburban area that consists of single RTU per apartment/house for SG traffic and an average 3.7 people per habitat, each with their user equipment, using one of the available carriers. Normal SG traffic is generated in both directions, uplink and downlink. The worst-case usage factor is considered as a power outage, where all SG meters in the area of influence simultaneously detect and attempt to report such a failure. Thus, emergency SG traffic is generated simultaneous by all RTUs. To alleviate the problem of the high momentary SG emergency traffic load, two distinct solutions are proposed and simulated. As the first solution, an artificial, up to one-second random delay is introduced in the transmission scheduling of emergency messages. The second solution applies low-power WSNs at the cluster level and cluster heads that contain both 802.15.4 and LTE communication interfaces, i.e., a hybrid sensor-LTE network. The simulation results show that both of the solutions that try to alleviate the high instantaneous traffic loads can reach the quality of service criteria for SG traffic without compromising other public LTE traffic. The deciding factor to use either pure LTE approach or a hybrid sensor-LTE network comes from non-functional requirements of the system.

Long Term Evolution (LTE) and Long Term Evolution-Advanced (LTE-A) support a better data transmission service than 3G dose and are globally commercialized technologies in a cyber world that is essential for constructing a future mobile environment, since network traffics have exponentially increased as people have started to use more than just one mobile device. However, when User Equipment (UE) is executing initial attach processes to access LTE networks, there is a vulnerability in which identification parameters like International Mobile Subscriber Identity (IMSI) and Radio Network Temporary Identities (RNTI) are transmitted as plain texts. It can threat various services that are commercialized therewith in a cyber world. Therefore, a security scheme is proposed in this paper where identification parameters can be securely transmitted and hidden in four cases where initial attach occurs between UE and Mobility Management Entity (MME). The proposed security scheme not only supports encrypted transmission of identification parameters but also mutual authentication between Evolved Node B (eNB) and MME to make a secure cyber world. Additionally, performance analysis results using an OPNET simulator showed the satisfaction of the average delay rate that is specified in LTE standards.

The article focuses on the design, measurement, and simulation of a new Long Term Evolution (LTE) downlink mode in which the polarization diversity replaces the spatial diversity at the user equipment (UE). The proposed system enables the analysis of the circularly polarized (CP) antenna over the multipath SISO channel. The purpose of the article is to design a compact LTE SISO system capable of providing comparable performance to the one with spatial diversity (SIMO 1 × 2). In this respect, the entire process is described from antenna designing and measurements to the final stage of integration and simulation. The results indicate the necessity of taking into account the effect of the polarization diversity to keep up the data rate for the small LTE devices when spatial diversity is not an option. The new system proves valuable to evolve toward new downlink modes suitable especially for tiny devices yet capable of achieving high data rates. The article envisages some new processing stages at the UEs as well as at the base station (eNodeB) for CP usage. © 2016 Wiley Periodicals, Inc. Int J RF and Microwave CAE 26:547–558, 2016.

The UE-to-Network Relay functionality was introduced to Long Term Evolution (LTE) cellular networks by the 3rd Generation Partnership Project (3GPP) in Release 13. In this technology, User Equipment (UEs) acting as Relay UEs are used to extend network coverage to cell-edge and out-of-coverage Remote UEs. One important part of this functionality is direct discovery, which is used by the Remote UEs willing to reach the network to detect the Relay UEs in proximity that can provide the desired connectivity service. In this paper, we study this protocol considering both discovery models defined in the LTE standard, and we develop analytical models to characterize the average time a Remote UE takes to discover a Relay UE using each discovery model. We validate the analytical models using system level simulations and we study the sensitivity of the metrics to different parameters of the protocol and number of UEs involved in the UE-to-Network Relay discovery.