Next Generation Cellular Networks and Green Communication Pimmy Gandotra Student Member, IEEE SMVDU Katra, India
[email protected]
Rakesh Kumar Jha Senior Member, IEEE SMVDU Katra, India
[email protected]
Abstract—The intensifying subscriber demands have resulted in an evolution in the wireless communication networks (WCNs), sporadically. The fifth generation (5G) WCNs, currently in their embryonic stage, are undergoing standardization and are expected to be accessible in 2020. The unraveling technology is sufficient in meeting the subscriber demand for high data rate, but this is achieved at the cost of risen carbon footprint and harmful radiations into the environment. To overcome its detrimental impact on the environment and human health, the WCNs broach GREEN communication, i.e. Globally Resource Optimized Energy-Efficient Network. Various technologies, aid in acquiring the objective of GREEN communication in WCNs, including device-to-device (D2D) communication, ultra-dense networks (UDN), massive MIMO, spectrum sharing (SS) and the Internet of Things (IoT). This research proposal aims to outline these technologies and contribute towards GREEN communication, a protuberant topic of research in the current scenario. Another important aspect addressed in this proposal is to make use of these technologies for prolonging the battery lifetime of mobile terminals, thereby optimizing the network performance, as well as user terminal’s battery life, energyefficiently.
power control, and optimize the cellular network performance in a cost-effectively, maintaining a balance between ecologic and economic concerns. They focus on flat energy consumption and can abate considerable carbon dioxide (CO2) levels. The Information and Communication Technology (ICT), aims at abating almost 30% CO2 levels by 2030. These technologies support reduction in the Specific Absorption Rate (SAR), lessening the impact of harmful radiations on human health. Apart from the concern of rising CO2 levels into the atmosphere, another perilous issue in the WCNs is the battery lifetime of handsets. Though, various technologies optimize the network performance in terms of Quality of Service (QoS) and energy-efficiency (EE), the battery technology is not advancing at the same stride. Achieving network and device efficiency both, are paramount, for a GREEN 5G WCN. Both these aspects are addressed in this proposal. II. STATE OF THE ART Though 5G aggregates numerous technologies for meeting the rising subscriber demands, device-to-device (D2D) communication network is chosen here, for optimal allocation of the scarcely available resources. Operating mode of users, which may be cellular or D2D, is initially identified [2], and then RBs are allocated to the D2D users, after obtaining the channel state information (CSI) between the two. Since D2D users share spectrum with the cellular users, a high susceptibility of interference exists between the two types of users. Interference mitigation is effectively addressed through optimal RB allocation. A number of resource allocation algorithms are available in literature. Some of these have been discussed in [3] and [4]. Since an era of UDNs is awaited in the growing 5G WCNs, the count of users, and that too D2D users will be immense, resulting in profound interference problem. This problem can be effectively dealt, with the use of sectored antennas at the BS [5], boosting the throughput [6], [7], improving QoS and EE. Since the transmit powers will be risen in the 5G networks, the rate of battery drainage of the mobile handsets will be reckless. A proposal for prolonging the battery lifetime of the user terminals is stated here, using SS [1].
Keywords—Fifth generation (5G) cellular networks, green communication, Device-to-Device (D2D) communication, Ultra Dense Networks (UDNs), Massive MIMO, Spectrum Sharing (SS), Internet of Things (IoT), battery lifetime, energy-efficiency
I. INTRODUCTION Due to maturing of the 4G networks, research on 5G networks has accelerated, paving way for a massively connected WCN in near future. Such prodigious connections and count of devices results in large transmit powers, increasing the carbon footprint to extreme levels. The carbon footprint until 2020 has been projected in [1], and it is a significant percentage. This makes it necessary for the cellular networks to revolutionize, and head towards green communication. Since term ‘GREEN’ stands for Globally Resource Optimized Energy Efficient Network, this research, thus, focuses on optimal resource allocation, for an energy efficient cellular network with improved performance. For efficiently meeting the subscriber demands, 5G WCNs amalgamate various technologies, like device-to-device (D2D) communication, massive MIMO, ultra-dense networks (UDNs), spectrum sharing, Internet of Things (IoT). Meeting the intensive demands by scaling up the power levels is an unfavourable choice, both, for the ecology, as well as the mobile network operators. The 5G technologies, thus, address
III. RESEARCH PROPOSAL This proposal addresses optimal resource allocation in a 5G D2D network, and battery lifetime enhancement of a mobile terminal.
5G and IoT Lab, and SMVDU, TBIC, at Shri Mata Vaishno Devi University, Katra.
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two. The proposed scheme states that if favorable channel states are iteratively being provided by the mth cellular user, for different pairs in D, throughputs, as a result of RB sharing with mth cellular user, will add in consecutive iterations, boosting the QoS. At some instants, throughput may fall for a high pair count, due to large interference incurred by a pair, from its adjacent pairs. Details on these can be obtained from [8].
A. Optimal Resource Block Allocation For optimal RB availability, a novel architecture has been proposed in Fig. 1, emphasizing the use of sector antennas at the BS, sectorizing the cellular coverage for reduced interference and improved performance. Considering T number of users per sector, a set of D2D users, cellular users and RBs, D={1,2,…,d}, C={1,2,…,c}, and ϒ={1,2,…r}, is considered, with each cellular user allocated r RBs by the BS. D2D pairs require an optimal RB count, such that its demanded application is effectively met. The received SINR for nth pair, sharing kth RB from mth cellular user, is given as īn k,m =(pn k,m hn k,m)/ (N+In)
The total power consumed by the nth pair can be given as Pn=В ϕk pn k,m +Pckt (4) where В denotes the drain efficiency of the power amplifier. Computing EE as the ratio of throughput to power consumed, EE is given as EEn=Rn/Pn (5) The total EE can be computed as sum of individual EEs of the pairs.
(1)
th
The n pair suffers interference In, from its adjacent pairs within some range, from the BS, and also from the unshared RBs, contained with the cellular users participating in RB allocation, as shown in Fig. 1. Thus, In=ϕpn’ k,m hn,n k,m+ pbs hbs,nk,m+ ϕpm k’ hm,n k’,m k,m
B. Proposed Model for Battery Lifetime Enhancement With increasing count of primary receivers (PRs) in a SS network, connected to one primary transmitter (PT), the PT’s battery drains speedily, as depicted in Fig. 2. Considering a set of STĺSR pairs, , +1, +2, battery life of PT is proposed to be prolonged through appropriate selection of the ST, depending on the number of PRs to be served.
(2)
k
and pm denote the transmit powers of the nth Here, pn D2D transmitter and mth cellular user, over k and k’ RBs, pbs denotes the BS’s transmit power, hn k,m denotes the nth pair’s channel gain over kth RB, N denotes the AWGN noise power, such that CN~(0,1) and the channel gains of interference are denoted by hm,n k’,m, hbs,nk,m and hn,n k,m. Depending on RBs allocated, the throughput achieved by nth pair is given as, Rn=ϕk log2(1+ īn k,m)
Upon transmitting over a direct link between PTĺPR for some duration, the battery remaining with the PT can be computed as
(3)
th
Bremaining=Btotal - RPTĺPR (Pckt + PPTtx)
th
The selection of m cellular user, for RB allocation to n pair, is performed on the basis of the channel gain between the
where Btotal denotes the total available battery power at the PT, RPTĺPR denotes the rate achieved over the PTĺPR link, PPTtx denotes the PT’s transmission power, and Pckt denotes its circuit power consumption. If Bremaining falls below the threshold battery power level, the PT is liable to stop working. It then seeks ST’s cooperation.
Resource Block Allocation link Information Relaying Link Cellular Communication Link D2D Communication Link V2V Communication Link Interference Link between pairs D1, D2, …..Dd Number of D2D pairs in a sector C1, C2, …..Cc Number of cellular users in a sector
As shown in Fig. 2 (a), for a single PTĺPR link, ST (STJ) here) with least battery level availability can be used for information relaying. Slightly higher battery level of ST (STJ+1) can relay information for two PTĺPR links, and highest ST . (ST(J+2)) can relay for three PTĺPR links. Such a strategy will avoid dying out of the PT’s battery, before information transmission over the links.
D1 h1k,3 h3,1k’(3)
Cellular User D2D Pair
Relay Node
D2 h2k,1
C3
C1
h1,2k’(1) D3 k,5 h3 Radio Resource Allocation h5,3k’(5)
C4
C5
Tri-Sector Base Station
Ultra Dense Network (UDN)
C. SIMULATION RESULTS Using MATLAB, and LTE standard parameters for simulations, the proposal for optimal RB allocation is analysed. The achievable throughput values are depicted in Fig. 3, for d=3, for each T=30, 50 and 100, assuming low, moderate and dense user count in a sector, which shows rise in throughput in successive iterations, with rising user count. Lower throughput achieved for T=50 is due to large interference from adjacent D2D pairs, reducing SINR, and thus throughput. EE is analysed for the same case, as shown in Fig. 4. Higher EE is obtained, with rise in user count. Similar cases can be studied for variable values of d, and various parameters can be analysed.
C2
Cellular User
(6)
Dd
Vehicle-toCc Vehicle Smart Communication Transportation
UDN
Fig. 1. Proposed Model for Optimal RB Allocation in a 5G WCN, using D2D communication
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Information Relaying through appropriate secondary transmitter Secondary Communication Links PT ~ PRIMARY TRANSMITTER PR ~ PRIMARY RECEIVER ST ~ SECONDARY TRANSMITTER SR ~ SECONDARY RECEIVER
Battery availability
ST(J)
