LTE OPTIMIZATION AND MOBILE NETWORK

Transcription

1 FUTUREMOBILE COMMUNICATION: LTE OPTIMIZATION AND MOBILE NETWORK VIRTUALIZATION Yasir Zaki, Andreas Timm Giel,, Carmelita Görg University of Bremen, Technical University of Hamburg Euroview July 23 rd 2012 Outline Motivation of Wireless and LTE Virtualization LTE Virtualization Framework Simulation Model Contract Based Framework Simulation Configurations and Results Conclusion and Outlook 2

2 Motivation of Wireless and LTE Virtualization LTE Virtualization Framework Simulation Model Contract Based Framework Simulation Configurations and Results Conclusion and Outlook 3 Wireless Virtualization Wired virtualization is well known A natural extension from wired to wireless virtualization Virtualization of the wireless airinterface interface is a scheduling problem: Tx/Rx power Frequency, Time, Code Space allocation Similar to the well known wireless transmission strategies: FDMA, TDMA, CDMA and SDMA But virtualization is doing more 4

3 Motivation Behind Mobile Network Virtualization Mobile networks are one of the fastest growing technologies has big influence on our daily activities Often, the wireless resources of mobile networks are expensive and scarce Bi Being able to share and optimize i the resources usage is highly hl motivating Network virtualization is a good solution : reduces the number of base stations (reduce energy usage) allows completely new value chains (mainly smaller players) In addition, sharing the frequency resources among multiple operators is very appealing gives operators the flexibility to expand/shrink their networks on the fly 5 LTE Virtualization Virtualizing the LTE network means to virtualize the infrastructure of the LTE system This allows multiple network operators to create their own virtual network depending on their requirements and goals The challenges are: How to virtualize the physical infrastructure? What kind of changes are required to the existing LTE system? We mainly foresee two different types of virtualization processes: Virtualizing LTE physical nodes (e.g. enodebs, routers, Ethernet links) Virtualizing the air interface of the LTE system (focus of this presentation) 6

4 Motivation of Wireless and LTE Virtualization LTE Virtualization Framework Simulation Model Contract Based Framework Simulation Configurations and Results Conclusion and Outlook 7 LTE Air Interface Virtualization In order to virtualize the LTE air interface, the enodeb (LTE base station) has to be virtualized Our solution is inspired by the XEN 1 architecture, where mainly a Hypervisor is added on top of the physical resources. The hypervisor is responsible for virtualizing the enodeb and scheduling the air interface (OFDMA) resources among the Virtual Operators (VOs) 1 XEN is a node virtualization software 8

5 LTE Hypervisor It is responsible for: virtualizing the enodeb scheduling the air interface resources among the Virtual Operators (VOs) Physical enb Physical Resources PRBs Channel Conditions It collects all relevant information (from all VOs) : users channel conditions traffic load VO requirements VO contracts etc. Hypervisor (2nd level Scheduler) Virtual enbs LTE MAC LTE MAC LTE MAC Scheduler Scheduler Scheduler Based on that, the hypervisor tries to allocate the resources to the VO 9 Motivation of Wireless and LTE Virtualization LTE Virtualization Framework Simulation Model Contract Based Framework Simulation Configurations and Results Conclusion and Outlook 10

6 OPNET Simulation Model Physical enb Hypervisor Virtual enbs 11 Motivation of Wireless and LTE Virtualization LTE Virtualization Framework Simulation Model Contract Based Framework Simulation Configurations and Results Conclusion and Outlook 12

7 LTE Contract based Spectrum Management We defined four different types of contracts that the infrastructure provider offers to the virtual operators and these are: a) Fixed guarantees b) Dynamic guarantees c) Best effort (BE) with min guarantees d) Best effort with no guarantees 13 Continue In order for the hypervisor to be able to satisfy the operator requests and their predefined contracts, an estimate of the actual needed spectrum of each operator is required The operators need to feedback this estimate value back to the hypervisor (in a predefined time interval) The PRBs estimate of each operator can be calculated iteratively as follows: Where: n 1 PRBsTTI n (1 ) E( n) E E(N) is the averaged required PRBs count (estimate of the required bandwidth) over N time interval PRBsTTI(N) is the instantaneous PRBs count at the Nth TTI calculated by summing the PRBs that were additionally needed to schedule the un served users within this TTI N is the number of TTIs in the hypervisor interval α is the smoothing factor indicating the weighting 14

8 Motivation of Wireless and LTE Virtualization LTE Virtualization Framework Simulation Model Contract Based Framework Simulation Configurations and Results Conclusion and Outlook 15 Simulation Configurations The simulation is configured with 4 virtual operators each is configured with one of the different contract types defined earlier: Virtual Operator VO1 (Video streaming) Contract details fixed guaranteed contract of 33 PRBs VO2 (VOIP) dynamic guaranteed contract, with a max value of 33 PRBs VO3 (VOIP + BE Video on demand) VO4 (Small VOIP operator) best effort with min. guarantees contract, with min. and max. value of 25 and 45 consecutively BE and no guarantees contract Two scenarios are configured one without virtualization legacy and one with virtualization virtualized. 16

9 Simulation Configurations Parameter Assumption Number of VO 4 Number of virtual enodebs Total number of PRBs Number of active users Mobility model Channel model DL VOIP traffic model DL Video traffic model Hypervisor resolution, estimation factor α Simulation time 4 enodebs (one per VO) 99 (corresponds to about ~ 20 MHz) VO1: 12 video users VO2: 40 VOIP users VO3: 16 VOIP + 16 video users VO4: 3 VOIP users Random Way Point (RWP) with 5 km/h ITU Ped-A Silence/Talk Spurt length = neg. exp. with 3 sec mean. Call duration = uniform (1, 3 min) Inter-repetition time = negative exponential with 90 sec mean Video conferencing application with unlimited duration In/Outgoing stream inter arrival time = Const ( sec) In/Outgoing stream frame size = Const (80 Bytes) 1 sec, with sec 17 Virtual Operator (VO) allocated number of PRBs The figure shows the number of PRBs that each VO has been allocated over time It can be noticed that for the first operatortheprbs the allocation is fixed to 33 PRBs since it is using the fixed guaranteed contract For the other three operators we can notice that the allocated numberofprbs changeswithtime time depending on the traffic load and the contract details of each operator 18

10 Virtual operator 1 (12 video users) Air interface throughput and app. end to end delay What can be noticed is that the operator has the same performance with and without virtualization; this is because this operator has a contract with a guaranteed fixed allocation 19 Virtual operator 2 (40 VOIP users) Air interface throughput and app. end to end delay What can be noticed is that the operator has the same performance with and without virtualization 20

11 Virtual operator 2 Downlink used number of PRBs vs. time The previous results showed that operator 2 has the same performance with and without virtualization But, in the virtualized case VO2 is not wasting the air interface resources since it only uses the required number of PRBs to serve the users as can be seen above This is a big advantage since the operator will be able to cut cost because he will only pay for the resources used 21 Virtual operator 3 Application end to end delay We can see that similar performance is achieved in both cases for the VOIP users (left side). As for the video users (right side), they are suffering from huge delay in the legacy scenario due to buffering; whereas in the virtualized scenario they are having good performance. The reason why the VOIP users in the legacy scenario are not affected is the fact that these users are being served with higher priority and the resources are enough to serve those users, but not enough to serve the video users. 22

12 Virtual operator 4 (3 VOIP users) Air interface throughput and app. end to end delay One additional advantage that can be achieved in the virtualized scenario is the ability to serve small operators with relatively smaller number of users in a pure best effort manner with whatever resources are left rather than wasting these resources 23 Motivation of Wireless and LTE Virtualization LTE Virtualization Framework Simulation Model Contract Based Framework Simulation Configurations and Results Conclusion and Outlook 24

13 Conclusion and Outlook The simulation results showed that a better performance can be achieved by using network virtualization in the LTE system. Based on the contract configurations and the traffic load of each virtual operator the air interface resources are shared among the VOs. The overall resource utilization is enhanced and the performance for both the network and the end user is better. Both operator 2 and 3 benefited from virtualization mainly by being able to cut costs and providing better performance for their users. The results also showed the possibility of opening the market to new players (small operators) that can serve a specific role and have small numbers of users. 25 THANKS FOR LISTENING ANY QUESTIONS

14 BACKUP SLIDES Long Term Evolution (LTE) LTE is the latest evolution of 3GPP standard. Its based on Orthogonal Frequency Division Multiple Access (OFDMA) in the downlink and Single Carrier FDMA (SC FDMA) in the uplink Its a very good candidate to be considered for applying network virtualization LTE s new network architecture is based on a cost efficient two nodes architecture Enhanced NodeB (enodeb) Access Gateway (AGW) 28

15 BE Virtual Operators Allocation The allocation of the left PRBs to the BE operators in step 4 will be done based on a Fair Factor (FF) which is defined as follows: FF i E n # BE _ VO j1 E i n j PRBs _ alloc i int FF Left _ PRBs i Where: # BE_VO is the number of best effort virtual operator PRBs_alloci is the allocated PRBs for operator i Left_PRBS is the number of PRBs left after allocating VO of contract type a, b and the min guarantees of type c 29 Virtual Radio* Defines a framework for configurable radio networks It extends the network virtualization i concept into the wireless domain known as radio virtualization Different virtual radio networks can operate on top of a common shared infrastructure and share the same radio resources It presents how the radio resource sharing can be performed efficiently without interference bt between the different virtual it radio networks * J. Sachs, S. Baucke, Virtual Radio-A Framework for Configurable Radio Networks ; WICON 08, Hawaii, USA, Nov

16 VANU MultiRAN* Vanu MultiRAN ltiran Virtual Base Station is a commercial software Taking advantage of Vanu software RAN technology, MultiRAN was developed dto support multiple virtual base stations (vbts) running on a single BTS hardware platform. The expense of antennas, BTS electronics, and backhaul can all be shared. * J. Chapin; Overview of Vanu Software Radio ; from June LTE Downlink Physical Resource Structure Inter-carrier subspacing 15 khz Sub-carrier Frequency 12 Subcarriers (Hz) 12*15k=180kHz 32