- Wednesday, 14 June, 16:00-17:30, Room Theatre Attic Studio
- Session Chair: Antti Tölli (University of Oulu, Finland)
Sofonias Hailu (Aalto University, Finland); Mikko Säily (Nokia Bell Labs, Finland)
User Equipment (UE) paging and location tracking are influenced by the underling state handling model. There are recent proposals to introduce a new RRC state called RRC Inactive as a main state for inactive UEs in 5th Generation (5G) cellular systems. One of the characteristics of the new state is that the interface between the Radio Access Network (RAN) and Core Network (CN) is kept. Considering this characteristic, there are proposals for a RAN controlled paging and location tracking schemes for RRC Inactive UEs. In this paper, we show that this approach is not always beneficial, especially for high mobility UEs. Instead, we propose a hybrid paging and location tracking scheme where both RAN and CN are involved in the paging and location tracking of RRC Inactive UEs. This is done transparently to the UE. We further propose a hierarchical paging and location tracking scheme to reduce the signaling overhead from paging and location tracking updates. This scheme is applicable to both RAN based and CN based paging and location tracking schemes.
Mohammad Shehab, Endrit Dosti and Hirley Alves (University of Oulu, Finland); Matti Latva-aho (UoOulu, Finland)
This paper analyzes the effective capacity (EC) of delay constrained machine type communication (MTC) networks operating in the finite blocklength (FB) regime. First, we derive a closed form mathematical approximation for the EC in Rayleigh block fading channels. We characterize the optimum error probability to maximize the concave EC function and study the effect of SINR variations for different delay constraints. Our analysis reveals that SINR variations have less impact on EC for strict delay constrained networks. We present an exemplary scenario for massive MTC access to analyze the interference effect proposing three methods to restore the EC for a certain node which are power control, graceful degradation of delay constraint and joint compensation. Joint compensation combines both power control and graceful degradation of delay constraint, where we perform maximization of an objective function whose parameters are determined according to delay and SINR priorities. Our results show that networks with stringent delay constraints favor power controlled compensation and compensation is generally performed at higher costs for shorter packets.
Yanpeng Yang and Ki Won Sung (KTH Royal Institute of Technology, Sweden); Jihong Park (Aalborg University, Denmark); Seong-Lyun Kim and Kwang Soon Kim (Yonsei University, Korea)
In an Ultra-dense network (UDN) where there are more base stations (BSs) than active users, it is possible that many BSs are instantaneously left idle. Thus, how to utilize these dormant BSs by means of cooperative transmission is an interesting question. In this paper, we investigate the performance of a UDN with two types of cooperation schemes: non-coherent joint transmission (JT) without channel state information (CSI) and coherent JT with full CSI knowledge. We consider a bounded dual-slope path loss model to describe UDN environments where a user has several BSs in the near-field and the rest in the far-field. Numerical results show that non-coherent JT cannot improve the user spectral efficiency (SE) due to the simultaneous increment in signal and interference powers. For coherent JT, the achievable SE gain depends on the range of near-field, the relative densities of BSs and users, and the CSI accuracy. Finally, we assess the energy efficiency (EE) of cooperation in UDN. Despite costing extra energy consumption, cooperation can still improve EE under certain conditions.
David Martín-Sacristán (Universitat Politècnica de València & iTEAM Research Institute, Spain); Carlos Herranz (Universitat Politècnica de València, Spain); Jose F Monserrat (Universitat Politècnica de València)
Ultra-reliable V2V communications with extreme transmission rate probably constitute the most ambitious use case of the fifth generation mobile. At present, both the scientific community and the standardization bodies are addressing the design of the technologies that will make it possible, although there is no unanimity in which technologies to incorporate. This paper approaches this topic from the work developed in the METIS-II project, describing the use case, the technology enablers and some details of the evaluation of these techniques in realistic scenarios. Results show that, for a baseline system, carrier bandwidths needed to fulfil the requirements are between 30 and 100 MHz, depending on the scenario. Nevertheless, results show potential to reduce the needed bandwidth to a range between 20 and 50 MHz by incorporating additional technology enablers to the studied baseline system.
Mohammed Al-Imari (Samsung R&D Institute UK, United Kingdom (Great Britain))
One of the challenges facing the deployment of massive machine type communications in mobile networks is the overload in the radio access. When high number of devices attempt to access the system in a random access procedure, a collision happens and the transmitted data will be lost. As the base-station is not aware of how many users are colliding, it will not be able to resolve the collision. In this paper, we propose a method that enables the base-station to detect the number of colliding users in random access schemes. The proposed method capitalizes on the unique feature of frequency quadrature amplitude modulation (FQAM) that the number of active subcarriers in a FQAM symbol depends on the number of users transmitting on that symbol. Thus, in the proposed method, FQAM will be used by the users for the random access, and the base-station will estimate the number of colliding users based on the number of active subcarriers. We provide in details the channel structure, procedures and theoretical derivation of the average number of active subcarriers. Numerical simulations show that by using the proposed method the number of colliding users can be accurately detected at the base-station. Furthermore, it is shown that, with the knowledge of the number of colliding users, the base-station can successfully retrieve the users' data, and the performance of the random access schemes can be significantly enhanced.