Resource Allocation In LTE Advanced For Different Services

Amity Journal of Computational Sciences (AJCS)ISSN: 2456-6616 (Online)Volume 1 Issue 2Resource Allocation in LTE Advanced for DifferentServicesNeeraj Kumar1, Anwar Ahmad2ECE Department, Jamia Millia Islamia, New Delhi1neeraj.mohiwal@gmail.com, 2aahmad4@jmi.ac.in1,2Abstract:Communication system can perform different types ofservices in communication network. LTE-Advanced systemallocates radio resources for these services through a radioresource manager (RRM). Different types of services, suchas real time (RT) services, non-real time (NRT) services,control signalling, are dynamically active in network andtherefore these services require dynamic resource allocationfor transmitting corresponding data packets. A scheduler inRRM needs to satisfy demand of these services with limitedradio resources. Therefore, scheduler should be efficient inperforming radio resource allocation in such dynamicenvironment. Current paper proposes, in a LTE-Advancednetwork, a resource scheduling method for managingdifferent services. Proposed method tracks adaptivebehaviours of communication services based on number ofactive users, data buffer status, channel condition. Results ofproposed method are compared with existing methods and itis shown that current solution provides better results thanexisting methods.axis alre divided into number of sub-carriers. Resourceelement (RE) is a smallest resource unit, which occupies asingle sub-carrier and an OFDM symbol. A resource block(RB) is a minimum resource allocation unit to any singleuser. One resource block occupies 12 sub-carriers and 6/7OFDM symbols. Therefore, a resource block can have total72/84 resource elements. The technology supports flexiblebandwidths such as 1.4MHz, 3MHz, 5MHZ, 10MHz,15MHz and 20MHz. Each bandwidth can have differentnumber of resource blocks i.e. 6, 15, 25, 50, 75 and 100resource blocks (RBs) respectively. LTE standard suggestsfive different physical channels in downlink, which arePDCCH, PDSCH, PBCH, PCFICH, and PHICH [1].PDCCH channel is a control channel and PDSCH channel isa shared data traffic channel. Number of resource blocks areallocated to these channels in 1ms transmit time interval(TTI) sub-frame [2]. A LTE radio frame of 10ms containstotal 10 sub-frames, each of 1m. Each sub-frame [3] containstwo resource blocks (RBs) of 0.5ms duration. Figure 1suggests radio resource block structure according to LTEtechnology.Keywords: LTE-Advanced, service class, traffic, radioresource manager, resource scheduler.1. IntroductionLTE (Long Term Evolution) is a fourth generation (4G)technology is developed from GSM (2G) and UMTS(3G)telecommunication technology. LTE is a 3GPP standard.High mobile data utilization, mobile gaming, highmultimedia applications, web 2.0, mobile television etc. aremain inspiration to develop LTE (4G) standard. It provideshigh throughput up to 300MBPS in downlink and up to5MBPSin uplink. It is a complete packet switching (PS)system implementing an OFDM lecommunication Union (ITU)recommendation. So, it isnot a complete 4G technology, rather it is a 3.9G technology.Therefore, LTE is further evolved as per guidelines of ITUand called as LTE-Advanced (LTE-A) i.e. a true 4Gtechnology. LTE-Advanced provides up to 1GBPS data ratein downlink and up to 500 MBPS data rate in uplink. MIMO,relay technology, CoMP, carrier aggregation etc. providesuch higher data rate and low latency in LTE-A.In LTE, radio resources are divided into time and frequencyresource elements. Resource elements in time axis aredivided into number of OFDM symbols and in frequencyFig. 1. LTE resource block structure23www.amity.edu/ajcs

Amity Journal of Computational Sciences (AJCS)ISSN: 2456-6616 (Online)There are number of resource allocation methods areavailable in literature. Different survey papers suggest [4-6]different scheduling methods utilize in LTE. Figure 2suggests a general resource allocation block diagram. Radioresource manager (RRM) is a main component forscheduling resources. A packet scheduler or PDSCHscheduler allocates resources based on various parameterconsiderations, such as channel condition, buffer status,queue length, previous average data rate, fairness, delay etc.Volume 1 Issue 22. System Model & DesignScheduling model based on proposed method is shown infigure 3. In general, any scheduling model should beproposed such that it reflects practical environment ofnetwork. It should be reliable and flexible enough toaccommodate various services. Therefore, suggestedscheduling model utilizes poison traffic model for differentcommunication services. Poison traffic model [13] is anoldest and robust communication traffic model. In network,various types of services are presented, and scheduler shouldmanage its resources according to demand of services. Thesevarious services are type of various classes such as real time,not real time etc. There are mainly four types of serviceclasses as shown in table 1.Table 1: shows different types of service classes and theirexamplesFig. 2. A general traffic schedulerIn survey papers, various methods for resource schedulingare explained. Research paper [7] shows performancecomparison in basic techniques i.e. proportional fairness (PF)and round robin techniques. It suggests that PF techniqueprovides high fairness but moderate throughput. However, itdoes not differentiate service types for schedulingperspective. In [8], a way of improving QoS in proportionalfairness technique is suggested. Similarly, in [9] alsoadaptive QoS for PF techniques is described. However, thesetechniques have not vision to check active service typebefore resource scheduling. Dynamic service behaviourrequires dynamic resource allocation. In [10], different typesof service and their scheduling are described. It showsoptimization techniques for service prioritization in whichweights of service types are optimized. However, it does notconsider the traffic arrival rate, number of users, channelcondition etc. for resource allocation. Weighing factor-basedresource allocation is also explained in [11]. Data buffer andchannel information-based scheduling technique is describedin [12], which does not consider service types for scheduling.In network, a scheduler should consider service type, itsarrival rate, data queue length and number of active users inresource allocation. Current paper proposes a resourcescheduler having inter-class scheduler and intra-classscheduler. The scheduler schedules resources based onarrival rate, data queue length and number of active usersand channel conditions.Service class typeExampleControl SignallingIMS signallingReal time (RT)VoiceNon real time (NRT)Streaming videoBest Effort (BE)Email, SMSIt is considered that current scheduler interacts with thesevarious types of services. Let, each service of class C hasmean arrival rate iswhich is represented in terms ofpoison traffic model. Further, each service of class type C isperformed by number of useswith total data packetqueue length . The poison traffic model equation for anyservice class Cis defined as shown in equation 1.(1)To perform a service, it requires sufficient number ofresource blocks to transmit its service data packets. Numbersof resource blocks K are depending on available bandwidthin a network. The scheduler schedules K physical resourceblocks (RBs) to total M users corresponding to all services.Number of users, M, are sum of all users in each serviceclass type.Each service class C experiencesarrival rate throughusers, wherein each user of class C has its own data packetwhose packet queue length is defined as. Total packetlength of any service class Cis defined as below.As shown in figure 3, current scheduler consists of two typesof internal schedulers. One of the internal schedulers is an24www.amity.edu/ajcs

Amity Journal of Computational Sciences (AJCS)ISSN: 2456-6616 (Online)Volume 1 Issue 2inter service class scheduler which is followed by anotherinternal scheduler i.e. intra service classes scheduler. Interservice class scheduler allocates number of resource blocksfor each service class type based on total users, packet lengthand mean arrival rate.(8)where is a resource proportional constant, which value isbetween 0 to 1. Scheduler allocates the resources if(9)(10)(11)(12)Equation 12 shows similar structure as shown in equation 2for resource allocation. A priority matrix for different serviceprioritization is shown below.Fig. 3. Scheduler based on proposed methodFurther, intra service class scheduler allocates receivednumber of resource blocks to its users based on its userpacket length and channel condition. Current schedulerallocates resources if condition shown in equation 2 exists.(2)The BW is current bandwidth of system. There is mismatchmay exist, i.e. required numbers of resource blocks are moreor less than BW. Required numbers of resource blocks allservices are defined as in equation 3. Note that numbers ofresource blocks are depended on system bandwidth i.e.,.(3)Iffor number of services are less than bandwidthBW, then number of resource blocks are simply scheduled.However, iffor numbers of services are greater thanbandwidth BW i.e. condition shown in equation 4 exists, it isrequired to prioritize service classes, so that this abovementioned condition is avoided.(4)Service class prioritization is depended on arrival rate, queuelength and number of users. A service class C can havemaximum throughput is decided by bandwidth and signal tonoise ratio. Shannon Hartley theorem suggests maximumthroughput in equation. 5.(5)Theis a total arrival rate of all four types of servicesclasses i.e.(6)Expected throughput of all services of different classes isgiven by equation. 7.(7)(13)According to equation 12, the class-based priority matrix isgiven as in equation 14.(14)Priority matrixis designed in inter service classscheduler, so that it allocates total number of resourcesblocks individually for each service class type. The value ofis different for different service class types. Outputcorresponding to respective service class of inter serviceclass scheduler is given to respective intra service classscheduler. The intra service class scheduler receives totalnumber of resource blocks and allocates these resourceblocks to corresponding users. The resource allocation isvaried for each user based on experienced channel conditionand its data packet queue length. The user Resourceallocation metric of intra service class scheduler is given asin equation 15.(15)Theis current expected data rate of user i of serviceclass C andis average received data rate of user i ofservice class C.For the LTE-advanced network a user can be scheduled byRRM with number of carriers, so in resource blockallocation equation derived above can be for LTE-Advancednetwork. In equation, here, we are considering that there arefive carriers (maximum in carrier aggregation) can beallocating to users.The equation updated for carrier aggregation supportingusers is:25www.amity.edu/ajcs