Low-Feedback Multiple-Access and Scheduling via Location and Geometry Information Congzheng Han, Matthew Webb, Angela Doufexi, Mark Beach {Bernice.Han, M.W.Webb, A.Doufexi, Presenter: Simon Armour University of Bristol EE

Outline Introduction to ViewNet Purpose and technologies Applications Use of location information to develop Low-complexity beamforming and schedulers Feedback free proportional fair algorithm Conclusions

ViewNet ViewNet - rapid mapping and visualisation of previously unseen environments. Visual SLAM provides 3D local coordinates of a moving camera and instantaneously maps the surrounding environment based on observations within the video stream. Fusion of vision (VSLAM), relative (inertial sensors) and absolute localisation from UWB and GPS. Supported by mobile communication infrastructure, operating over multiple wireless technologies (Tetra, WiFi)

Scenarios Road-traffic accident Siege intel Gaming Fire & rescue Pre VIP visit

Wireless Enhancements ViewNet Application provides real time 3D location and environment information. Exploitation of location information for improved wireless capability. Single-user and multi-user beamforming Low-feedback, low-complexity multi-user schedulers for beamforming systems Location-based proportional fair algorithm

Location-Assisted Beamforming Beamforming allow different users to share the same spectral resources and achieve improved system capacity. An ordinary beamforming system requires additional bandwidth due to feedback overhead and processing time to obtain coordinates information. In ViewNet, coordinate information provides an opportunity for scheduler to point energy towards user(s) of interest with no or limited feedback requirement.

Location-based Multiuser Scheduler (LBS) Traditional scheduler: find users with lowest multi- user interference in all possible combinations. computationally intensive A novel location based scheduler LBS find the group of users who are spatially far away from each other reduce mutual interference and improved overall rate. No feedback, low complexity target user User 2 User 3 User 4 An example of the Location-based Multi-user Scheduler (LBS)

SINR-based Multiuser Scheduler with Location Information (SBS) Additional SINR information if available. An alternative reduced-complexity and sub- optimal rate greedy scheduler (SBS) The targeted terminal is initially chosen in a round-robin fashion. Add a terminal that maximises the overall rate to the chosen sub-set until no remaining terminals can further improve overall rate.

System and Channel Description Transmission techniqueOFDMA Transmission Bandwidth100 MHz Carrier frequency5 GHz FFT size1024 No. of occupied sub-carriers768 Guard interval176 Sub-carrier spacing KHz No. of sub-channels48 Averagae number of users25 Transmit power level17 dBm Noise figure-94 dBm ESTI BRAN model C – large open space NLOS and its corresponding path loss model for n. Scenario 1: All terminals experience equal received SNR of 0dB Scenario 2: Terminals at random locations in the range of m away from the BS. Terminals have different SNRs.

Multi-user Schedulers Increased array size improves both system rate and fairness by supporting more users. The simple feedback free location-based multi-user scheduler (LBS) achieves a significant percentage of the reference (SBS) rate.

Location-based PFA The selection of targeted user for LBS and SBS Greedy: favours strong users (closer to BS). Round-robin: degraded system rate. Modified proportional fair algorithm (PFA) for OFDMA system Traditional PFA requires rate/SINR feedback Proposed PFA only use location information, no feedback required.

Location-based PFA : current Tx-Rx distance between BS and terminal k Average Tx-Rx distance between BS and terminal k in a past window of length : C is the total number of sub-channels per OFDMA symbol, c is sub-channel index. Impose fairness constraints on user selection. Assumes terminals closer to the BS generally have better channel conditions Target user is selected based on:

Location-based PFA The algorithm schedules a terminal when its Tx-Rx distance is low relative to its own average Tx-Rx distance over the specified window length. As window length increases, the algorithm approaches to a greedy scheduler – select the closest terminal as the target user.

Location-based PFA By scaling the window length without introducing further feedback requirement, PFA allows significant fairness improvements in exchange for minor rate loss.

Conclusions ViewNet supports rapid 3D mapping of environment at low cost Wireless enhancements through utilisation of the location information No / reduced feedback multiuser schedulers for beamforming systems. New PFA based on location information showing significant fairness improvements in exchange for minor rate loss.

Conclusions The proposed location-based schedulers are applicable to any centralised system 3GPP LTE, WiFi, WiMAX, potential future generation communication systems, V2V and V2I communications. Another paper titled Wireless Schedulers with Future Sight via Real-Time 3D Environment Mapping in VTC prediction of future rate values and proposal of a family of novel scheduling methodologies taking advantage of environmental information provided by ViewNet

This work was co-funded by the UK Technology Strategy Board. We thank all the partners to the ViewNet project for their help and discussions.