Although the number of massive machine type communications (mMTC) devices covered by a fifth generation (5G) cell could be huge, not all devices are always active. For radio resource allocation, it is vital that a base station has the knowledge on the number of active mMTC devices in each frame. In this paper, we develop a mathematical framework to perform pseudo-Bayesian estimation on the number of active devices within a 5G new radio (NR) subframe. The estimation is performed by the base station on a subframe-by-subframe basis based upon which a transmission permission probability is imposed on active devices for their transmissions in the next subframe. The active devices include both backlogged devices and new arrivals in the current subframe that will attempt for medium access in the next subframe relying on a combination of NR radio resources in both time and frequency domains. Such an estimation constitutes an important component for the design of grant-free access schemes for mMTC uplink traffic.

Although grant-based mechanisms have been a predominant approach for wireless access for years, the additional latency required for initial handshake message exchange and the extra control overhead for packet transmissions have stimulated the emergence of grant-free (GF) transmission. GF access provides a promising mechanism for carrying low and moderate traffic with small data and fits especially well for massive machine type communications (mMTC) applications. Despite a surge of interest in GF access, how to handle heterogeneous mMTC traffic based on GF mechanisms has not been investigated in depth. In this paper, we propose a priority enabled GF access scheme which performs dynamic slot allocation in each 5G new radio subframe to devices with different priority levels on a subframe-by-subframe basis. While high priority traffic has access privilege for slot occupancy, the remaining slots in the same subframe will be allocated to low priority traffic. To evaluate the performance of the proposed scheme, we develop a two-dimensional Markov chain model which integrates these two types of traffic via a pseudo-aggregated process. Furthermore, the model is validated through simulations and the performance of the scheme is evaluated both analytically and by simulations and compared with two other GF access schemes.

The diversity of application scenarios in 5G mobile communication networks calls for innovative initial access schemes beyond traditional grant-based approaches. As a novel concept for facilitating small packet transmission and achieving ultra-low latency, grant-free communication is attracting lots of interests in the research community and standardization bodies. However, when a network consists of both grant based and grant-free based end devices, how to allocate slot resources properly between these two categories of devices remains as an unanswered question. In this paper, we propose a Markov decision process based scheme which dynamically allocates grant-free resources based on a specific reliability or priority requirement. The performance of the proposed scheme is evaluated via both analysis and simulations under various traffic arrival conditions.

Sensing is a fundamental aspect in cognitive radio networks and one of the most complex issues. In the design of sensing strategies, a number of tradeoffs arise between throughput, interference to primary users, and energy consumption. This paper provides several Markovian models that enable the analysis and evaluation of sensing strategies under a broad range of conditions. The occupation of a channel by primary users is modeled as alternating idle and busy intervals, which are represented by a Markov phase renewal process. The behavior of secondary users is represented mainly through the duration of transmissions, sensing periods, and idle intervals between consecutive sensing periods. These durations are modeled by phase-type distributions, which endow the model with a high degree of generality. Unlike our previous work, here the source of secondary users is nonsaturated, which is a more practical assumption. The arrival of secondary users is modeled by the versatile Markovian arrival process, and models for both finite and infinite queues are built. Furthermore, the proposed models also incorporate a quite general representation of the resumption policy of an SU transmission after being interrupted by PUs activity. A comprehensive analysis of the proposed models is carried out to derive several key performance indicators in cognitive radio networks. Finally, some numerical results are presented to show that, despite the generality and versatility of the proposed models, their numerical evaluation is perfectly feasible.

The performance evaluation of the random access (RA) procedure in LTE-A has recently become a major research topic as these networks are expected to play a significant role in upcoming 5G networks. Up to now, the key performance indicators (KPIs) of the RA in LTE-A have been obtained either by performing a large number of simulations or by means of analytic models that sacrifice precision in exchange of simplicity. In this paper, we present an analytic model for the performance evaluation of the LTE-A RA procedure. Using this analytic model, each and every one of the KPIs suggested by the 3GPP can be obtained with a minimal error when compared to the results obtained by simulation. To the best of our knowledge, this is the most accurate analytic model of the LTE-A RA procedure.

The performance evaluation of the random access (RA) in LTE-A has recently become a major research topic as these networks are expected to play a major role in future 5G networks. Up to now, the key performance indicators (KPIs) of the RA in LTE-A have been obtained either by performing a large number of simulations or by means of analytic models that, oftentimes, sacrifice precision in exchange for simplicity. In this paper, we present an analytical model for the performance evaluation of the LTE-A RA procedure that incorporates the access class barring (ACB) scheme. By means of this model, each and every one of the KPIs suggested by the 3GPP can be obtained with minimal error when compared with results obtained by simulation. To the best of our knowledge, this paper presents the most accurate analytical model, which can be easily adapted to incorporate modifications of network parameters and/or extensions to the LTE-A system. In addition, our model of the ACB scheme can be easily incorporated to other analytic models of similar nature without further modifications.

The number of devices that communicate through the cellular system is expected to rise significantly over the coming years. But cellular systems, such as LTE-A, were designed to handle human-to-human traffic. Hence, they are not suitable for managing massive machine-to-machine communications. Therefore, additional congestion control methods must be developed and evaluated. Up to date, access class barring (ACB) and extended access barring (EAB) methods are the preferred solutions for reducing congestion in the access channels of the evolved NodeB. These methods are based on restricting the access of certain classes of UEs, so the system capacity is not exceeded. Due to the high complexity of the LTE-A system, evaluating its performance is not straightforward. Specifically, a large number of variables, coexistent mechanisms, and test scenarios make it difficult to identify the network parameters that enhance performance. In this paper, we analyze the ACB method in highly congested environments. For this, we evaluate the effect of ACB parameters (barring rates and barring times) by means of several key performance indicators (KPI) such as delay, energy consumption (preamble transmission attempts required) and success probability. We observed that ACB is appropriate for handling sporadic congestion intervals in LTE-A networks.

Existing location management (LM) methods for macrocells in LTE-Advanced have tracking area list (TAL) granularity. Therefore, a user equipment (UE) triggers a location update (LU) whenever it leaves its current TAL, and it is searched through paging (PG) with TAL accuracy. However, these procedures are not well-suited for small cells (SCs). The reasons are twofold. First, dense deployments of SCs imply that paging has a low probability to be successful in the first attempt, increasing the signaling overhead in the core network (CN). Second, smaller coverage areas lead to a higher mobility among cells, increasing the signaling overhead in the CN due to LUs. In this work, two LM schemes with fine granularity are proposed. These schemes update UE's location to a local anchor (LA) in a SC or tracking area (TA) basis, respectively. By increasing the accuracy of UE's location, a significant reduction of signaling overhead in the CN due to PG is achieved. Moreover, LUs to the LA are performed through direct X2-interface links to avoid signaling overhead in the CN. A versatile mobility model is developed and closed-form expressions for UEs' mobility metrics are found to validate the proposed schemes through variations of critical parameters such as TA/TAL configuration, UE's mobility patterns and cell residence times.

A general framework of the movement-based location update with selective paging strategy is proposed in this paper. Each time the mobile terminal revisits the last cell it had contact, its movement-counter is increased with probability p or it is frozen (stopped) with probability q or it is reset with probability r, (p+q+r=1). This paper discusses the trade-off between the location update cost and the terminal paging cost, when selective paging is implemented, in terms of the set of parameters p, q and r.

In cellular systems, there is usually an overlap cell coverage area (area covered by two or more base stations) which has valuable practical applications: soft handoff is an important feature of CDMA systems, and in hard handoff, the overlap area allows the queuing of handover requests as a handover prioritization scheme. While an extensive research effort has been done to model the terminal residence time in a cell and the channel holding time, the sojourn time in the overlap area is a topic that still requires further study. We propose a model of the sojourn time in the overlap area, along with a novel numerical method to derive its probability distribution. The obtained results show that the common assumption of exponential distribution for this time is not suitable, whereas it can be satisfactorily fitted by the hyper Erlang distribution.

Mobility tracking operations in a personal communication service (PCS) system are signaling consuming. Several strategies have been proposed in the literature to reduce both the location update (LU) and the paging (PG) costs. In this paper, we propose a location-tracking algorithm called three-location area (TrLA), combined with selective paging. In TrLA, the mobile terminal (MT) allocates the identification of three neighboring location areas (LAs) in its local memory. We call this set of three LAs, a big-location area (BLA). Each time the MT exits the BLA, it triggers an LU message to the system databases via a base station, in order to maintain the databases up to date. The MT also updates its cache memory. A two-step selective PG is also considered and compared with the single-step (or nonselective PG). An analytical model based on a semi-Markov process has been used to evaluate our proposal. This scheme is compared with the classical Global System for Mobile Communications (GSM) standard and the two-location algorithm proposal. As a result, this new scheme outperforms the cited strategies, and in our opinion, it can easily be implemented in existing standard cellular and personal communication systems.

This paper deals with time-assigned speech interpolation (TASI) systems. We show that under the assumptions of an exponential distribution for both talkspurt and silence duration, and the first-in first-out (FIFO) discipline, the percentage of talkspurts totally cut off coincides with the well-known formula of Weinstein (1978). In addition, we provide the probability distribution function (PDF) of the portion that a talkspurt is cut off under the FIFO discipline.

The DECT (Digital European Cordless Telecommunication) system has been designed to be used in three different environments: domestic, telepoint and business. For the business one voice and data services have to be offered allowing one to build a wireless network with integrated traffic. The DECT basic channel is symmetric and has a transmission rate of 32 kbps. This channel seems not very suitable for data applications so the DECT standard defines some procedures to handle data traffic in a better way. These procedures allows one to create connection oriented (symmetric or asymmetric) communications with a higher data transmission rate. These channels are created using multibearer connections.>

Systolic architectures implement regular algorithms in hardware, in order to obtain high computational throughput. In this paper we provide a modular architecture for a deconvolution iterative algorithm. The basic module is a systolic array which implement one iteration of the algorithm recently proposed in [1]. The algorithm is a generalization of the method to invert non singular polynomial transfer function, previously published in [2]. The basic systolic module can be repeatedly concatenated in such a way that can be used in real time applications.

This paper is concerned with the inversion of digital singular convolution operators defined by a polynomial in the z-transform domain. For that purpose, in the one dimensional case (1D), the method given here proceeds by first approximating the polynomial by a rational transfer function, Which numerator results to be an autocorrelation functions, free of zeros on the unit circle. This is obtained by using the least square inverse concept of a polynomial. The extension to the 2D case, can be achieved using the well known 2D planar least square inverse polynomial (PLSI) in semicausal form. With this approach, the inversion deals with a non singular autocorrelation functions, so we can use the asymmtotical method given recently |1|.