1. Li-Fi Research and Development Centre University of Edinburgh
2nd ACM Workshop on Visible Light Communication Systems (VLCS 2015)
September 11, 2015, Paris, France
On Limited feedback Resource Allocation for Visible Light Communication Networks
Li-Fi Research and Development Centre
University of Edinburgh
Mohammad Dehghani Soltani, Xiping Wu, Majid Safari, Harald Haas
2nd ACM Workshop on Visible Light Communication Systems (VLCS 2015)

2. Agenda Importance of feedback (Throughput & Fairness)
Type of feedbacks
Optimizing Feedback (Maximize the overall throughput)
Proposed Limited Feedback Scheme
Some simulations
Conclusions
2nd ACM Workshop on Visible Light Communication Systems (VLCS 2015)

3. Importance of Feedback
The aim is to allocate resources elastically in time, spectrum and space, in order to accommodate a large range of traffic profiles and granularities in an efficient way.
Resources should be specified and this resources should be fedback to the access points
to core network
2nd ACM Workshop on Visible Light Communication Systems (VLCS 2015)

4. Limited Feedback Scheme
Types of feedback
Full Feedback Scheme
Users send the SINR of all subcarriers at the beginning of each frame
Limited Feedback Scheme
Each user sends the SINR of all of its subcarriers only once at the beginning of the first frame.
For the next frames, the users only update the scheduler with their average power (i.e., the DC channel component)
2nd ACM Workshop on Visible Light Communication Systems (VLCS 2015)

5. 𝛾 𝓁 𝑗 𝑘 = 𝛾 1 𝑗 𝑘 × 𝛾 𝓁 𝑗 0 𝛾 1 𝑗 0 Proposed Limited Feedback Scheme
SINR estimation
𝛾 𝓁 𝑗 𝑘 = 𝛾 1 𝑗 𝑘 × 𝛾 𝓁 𝑗 0 𝛾 1 𝑗 0
SINR of 𝑗th user at 𝓁th frame on the 𝑘th subcarrier
The frequency-selective characteristics of these devices are fairly static and in comparison to RF, they are independent of the user’s position or orientation. However, the average received power is much more dynamic and is significantly dependent on the position and the orientation of the users’ devices. Therefore, by only updating the average power, a reasonable estimate of the SINR of all the
subcarriers can be obtained.
2nd ACM Workshop on Visible Light Communication Systems (VLCS 2015)

6. 𝑅 𝑓 =𝒩 log 2 𝑀 𝑅 𝑓 =𝒩 𝒦 2 𝑙𝑜𝑔 2 𝑀 Limited Feedback Full Feedback
𝒩 : Number of user
𝑅 𝑓 =𝒩 log 2 𝑀
𝑀 : Constellation size
Full Feedback
𝑅 𝑓 =𝒩 𝒦 2 𝑙𝑜𝑔 2 𝑀
𝒦: Number of subcarriers
2nd ACM Workshop on Visible Light Communication Systems (VLCS 2015)

7. Simulation Results Bench marks: Proportional Fair (PF) Scheduler
Maximum channel quality indicator (CQI)
Simulation parameters
16 Access points, 10m × 10m Room, DCO-OFDM, LOS & NLOS, FoV (90°), …
Evaluation parameters
Throughput
User’s satisfaction
2nd ACM Workshop on Visible Light Communication Systems (VLCS 2015)

8. Total throughput for different resource allocation schemes with full and limited-feedback (average request data rate: 40Mbps and 80Mbps)
2nd ACM Workshop on Visible Light Communication Systems (VLCS 2015)

9. Average number of users who achieve at least 95% of their desired rate for different resource allocation schemes with full and limited-feedback (average request data rate: 40Mbps and 80Mbps)
2nd ACM Workshop on Visible Light Communication Systems (VLCS 2015)

10. Comparing CDF of user throughput for full and limited feedback approaches with 60 users (average request data rate: 40Mbps and 80Mbps)
2nd ACM Workshop on Visible Light Communication Systems (VLCS 2015)

11. Comparing CDF of user satisfaction level for full and limited feedback approaches with 60 users (average request data rate: 40Mbps and 80Mbps)
2nd ACM Workshop on Visible Light Communication Systems (VLCS 2015)

12. Future works CONCLUSION
Limited Feedback has a close performance to FF in Li-Fi network
Limited Feedback generates much lower feedback overhead
Future works
A heterogeneous network will be considered
Feedback update in technology specific network
SDN for intelligence resource assignment
2nd ACM Workshop on Visible Light Communication Systems (VLCS 2015)

13. Thank you for your consideration!
2nd ACM Workshop on Visible Light Communication Systems (VLCS 2015)