Presentation on theme: "Tarun Bansal*, Karthik Sundaresan+,"— Presentation transcript:
1 R2D2: Embracing Device-to-Device Communication in Next Generation Cellular Networks Tarun Bansal*, Karthik Sundaresan+,Sampath Rangarajan+ and Prasun Sinha*Speaker: Zhixue Lu**Ohio State University and +NEC Labs America
2 Device-to-Device (D2D) Communication Normally smartphones communicate with each other through cellular base stationWithout D2DWith D2D
3 D2D Traffic Applications (b) Peer-to-Peer:Public Safety when traditional infrastructure is not availableBenefit: No interference(a) Base Station Assisted:Localized communication and Machine-to-Machine (M2M) communicationBenefit: Service provider helps with security, neighbor discovery and ensuring Quality-of-ServiceOur focus is on integration of Base Station Assisted D2D Traffic withexisting cellular communication
4 Our analysis for sectored deployments: D2D BenefitsSpatial Reuse of ResourcesMultiple D2D transmissions per cell [Janis 2009, Doppler 2009, Lee 2013]Our analysis for sectored deployments:Very little benefit from additional spatial reuseD4D1D2D1D2D4Cell divided into 3 sectors with each sector covering 120oNot possible to schedule multiple D2D transmissions in the same sector.D3D3
5 D2D Benefits (contd.) Offloading Fewer time slots taken [Janis 2009, Doppler 2009, Lee 2013]Time slot 1Time slot 2Time slot 1Without D2DWith D2D
6 Benefit of D2D in sectored deployments (Static Channel Allocation) classifiedas cellularSpatial ReuseBenefitOffloadBenefitTries to schedule multiple D2D transmissions per sectorOffload benefit is significant (1 time slot instead of 2)Additional Spatial Reuse benefit (due to D2D) is not significant in sectored deployments due to small sector size
7 Identifying third D2D Benefit: Flexible Load Use as flexible loadResources need to be fixed in both Uplink and Downlink directionsIn practice, UL-DL traffic distribution varies both in space and time e.g. residential vs. commercial, morning vs. eveningD2D can go on either on the Uplink or Downlink resourcesUse resources that would have been otherwise wastedUplink FlowsDownlink FlowsD2D flowstimetimefrequencyfrequency
8 How do we maximize these two benefits? D2D BenefitsOffloading (1 time slot instead of 2)Use as flexible traffic (Place on either DL or UL resource)How do we maximize these two benefits?
9 Static vs. Dynamic Channel Allocation Interior ChannelsToo much traffic: Borrow channels from neighboring sectorsExterior ChannelsTwo co-located sectorscan have the same channelStatic ChannelAllocationDynamic ChannelAllocation leverages spatialtraffic variations
10 Challenges in Incorporating D2D with Dynamic Channel Allocation UL or DL communications (directional) can still go simultaneouslyD2D (omnidirectional) may cause interference to coexisting transmissions in sectored deployments (not considered before)Determining interference from D2D transmission requires knowledge of path loss between all users (costly).D1D2D3Similarly, D2D transmission cannot coexistwith UL or D2DD2D presents a new challenge: Transmissions may cause interference if co-located sectors are using the same resource.
11 D2D Interference (Dynamic Channel Allocation) classifiedas cellularLower throughputwith D2D due tocollisions amongneighboringsectorsOmnidirectional nature of D2D makes it non-trivial to schedule transmissions
12 ObjectiveHow to do dynamic resource allocation in multi-cell deployments with D2D traffic?How to schedule UL, DL and D2D transmissions while avoiding interference?Previous work only looks at resource allocation without D2D traffic, ORScheduling with D2D in single cell deployments with no sectorization.
13 R2D2 ContributionsA light-weight scalable solution (R2D2) that works at two different time-scalesPhase 1: Allocate resources to each base station at coarser time scale (cross-sectors)Phase 2: Allocate resources to each flow independently at each base station at finer time scale (co-located sectors) while avoiding interference
14 R2D2 ContributionsPractical: Works in sectored deployments with multiple cellsProposed multiple scheduling algorithms with provable guaranteesShowed using simulation results that proposed algorithms perform close to optimal in practice
16 Phase 1: Cross-Sectors Resource Allocation Objective: Allocate UL and DL resources across 3 sectors in each of the directionsProposed algorithm satisfies following properties:Flexibly places the D2D traffic on UL and DL resourcesLocalized and ScalableEnsure no interference across sectors belonging to different base stationsSee Paper for more constraints and detailed solution
17 Phase 2: Per-frame Scheduling Each sector was a part of different interfering set in Phase 1:Same resourcemay get assigned toco-located sectorsD2D3D1
18 Phase 2: Per-frame Scheduling (contd.) Schedule UL, DL and D2D transmissions such that total throughput is maximized while avoiding interferenceAssign a time-frequency resource block to each flow in the three sectorsChallenge: Path loss information between devices is unknown
19 Phase 2 Contributions See Paper for detailed solutions Scheduling algorithms at each Base Station:A greedy polynomial algorithm with approximation ratio of ½A faster greedy polynomial algorithm with approximation ratio of ¼More challenging since D2D can go on either DL resources or UL, but not bothA greedy polynomial algorithm with approximation ratio of 1/3Time-DivisionedSystemFrequency-DivisionedSystemSee Paper for detailed solutions
20 Simulation Setup Simulation with 19 base stations and 57 sectors Modeled practical parameters including path loss, shadowingOther algorithms simulatedR2D2 Low ComplexityD2D Dynamic Genie (Optimal, knows path loss information between all users)No D2D Dynamic (Uses dynamic resource allocation and classifies all D2D traffic as Cellular)Existing Algorithm Static (Uses static resource allocation and does not use D2D as flexible traffic, Janis et al., IJCNS 2009)
21 Results with variation in D2 traffic R2D2 Low Complexity performs within 5% of optimalR2D2 Low Complexity gives a throughput of 2.5x and 4.9x compared to existing solution and No D2D, respectivelyBenefits coming fromIntelligent resource allocation during Phase 1 while placing D2D traffic flexiblyInterference-free scheduling during Phase 2within5%2.5x4.9x
22 ConclusionsInvestigated the problem of incorporating D2D communication in next generation cellular deployments with sectorizationIdentified a new benefit of D2D communications: FlexibilityTowards that, proposed a solution that works at two different time granularities that ensures scalabilitySynergy between the two phases makes R2D2 light weight while avoiding all interferenceProposed multiple algorithms with provable approximation ratios for resource allocation and schedulingThank You