Recent papers

Here are some of my recently published papers

• Challanges and opportunities of mm-Wave communications in 5G networks, in Proc. CROWNCOM 2014                                                                                                                                              This paper provides an overview of research challenges and opportunities on mm-wave communication in the fifth generation (SG) mobile broadband networks. More specifically, different challenges, i.e. spectrum, propagation channel, cost and energy efficient aspects, from the perspective of mm-wave communication are discussed. Furthermore, insights on research opportunities of mm-wave communication in heterogeneous networks and multi-antenna transceiver technologies are provided. Based on provided overview, it can be concluded that mm-wave communication is a promising framework for further development and research towards next generation mobile broadband communication systems.

• Interference aware power control games for ISM bands, in Proc. CROWNCOM 2014                                                                                                                                            The use of wireless equipment in the already-overcrowded ISM bands had been further growing in recent years. This increase leads to high interference levels, which causes unstable communication and an average throughput reduction in heavily-used channels. This calls for more robust, interference-aware means of channel-access for Wi-Fi and similar wireless devices in ISM bands. In this paper, we propose a Game Theory (GT) based power allocation mechanism for IEEE 802.11 networks, which might incorporate some aspects of Cognitive Radio (CR) functionality. Up to now operation of 802.11 devices was constrained by regulations in terms of maximum transmission power, in order to limit the extent of interference from uncoordinated emissions. Our proposed mechanism, with its feasibility backed by the practical experimentation reported in this paper, would allow embracing lighter regulatory rules or complete abolition of power limits for unlicensed access in ISM bands. Moreover, our proposed concept of channel access based on power balancing game might also make unnecessary the use of CSMA/CA protocol.

• An iterative and truthful multi-unit auction scheme for coordinated spectrum white space shaing, in Proc. of the IEEE SIGMETRICS  2014 Joint Workshop on Pricing and Incentives in Networks and Systems

• Automatic trust computation for service oriented sytems, IET Software Journal, 2014                                                                                                                                               Among various service providers providing identical or similar services with varying quality of service, trust is essential for service consumers to find the right one. Manually assigning feedback costs much time and suffers from several drawbacks. Only automatic trust calculation is feasible for large-scale service-oriented applications. Therefore an automatic method of trust calculation is proposed. To make the calculation accurate, the Kalman filter is adopted to filter out malicious non-trust quality criterion (NTQC) values instead of malicious trust values. To offer higher detection accuracy, it is further improved by considering the relationship between NTQC values and variances. Since dishonest or inaccurate values can still influence trust values, the similarity between consumers is used to weight data from other consumers. As existing models only used the Euclidean function and ignored others, a collection of distance functions is modified to calculate the similarity. Finally, experiments are carried out to access the robustness of the proposed model. The results show that the improved algorithm can offer higher detection accuracy, and it was discovered that another equation outperformed the Euclidean function.

• Autonomous spectrum shaing in heterogeneous white space networks, in Proc. IEEE ICC 2013, Communications Workshops                                                                                                Regulation of cognitive radio access to spatially unused portions of TV spectrum (TV White Spaces (TVWS)) via a geolocation database was recently finalized in the US and is under way in the UK. Regulators elsewhere are also evaluating secondary use of TV and other bands. The question of how multiple potentially competing networks should share the TVWS spectrum is yet to be addressed. This is an important challenge as future deployment scenarios are expected to involve a heterogeneous mix of low-power and high-power, narrow-band and wide-band systems. This paper investigates through quantitative modelling aspects of heterogeneous spectrum sharing, taking as example TVWS sharing among low-power, e.g., the IEEE 802.11af standard, and high-power, e.g., the IEEE 802.22, standards.

 

Recent events where I present(ed)

Here is a list of some recent meetings where I presented/will be presenting

• IEEE ICUWB 2014, 1-3 September 2014, Paris

          -Keynote on  Technologies for unlocking spectrum above 6 GHz for 5G
        
           -Panel on mmW UWB Communication: A Key Enabler for 5G?

• IEEE  VTC 2014 (Spring), 18-21 May, Seoul,

          Panel on 5G Wireless

• IEEE WCNC 2014, 6-9 April 2014, Istanbul

          Executive Panel on "Beyond 10G"

Memory and interacting many-particle systems

 

Doing some computer experiments on learning algorithms in the context of wireless systems, I had some thought on the role of memory (another thing that trigged my interest was a paper I saw on magnetic holographic memory and also my on-off reading of "In Search of Lost Times" . 

 

The computer experiments were on sequential games, and we were looking at  a two-agent system, where each agent could make a move followed by a move by the other one. The very naive strategy that we first used was that at every move each agent would choose the action that would maximize its instantaneous pay-off. In this case the system just "flip-flopped"

 

• 1st agent chooses its best move according to the above strategy
•  This resultss in the worse outcome for the second agent
• Subsequently, the 2nd agent try to improve the situation by choosing the best move available
• This would then result in the worst outcome for the 1st agent

And the above cycle goes on without the system ever settling into any kind of equilibrium.

 

Obviously, none of the  agents had memory so could not forecast/predict that chosing the action with the best immediate payoff would result  in the next timestep in a bad payoff due to the oponent's response. Introducing memory can help the agents reach a compromise solution (at least if this exists, which was the case in our experiments) .

 

This made me think about one of the previous blogs that I posted quite a while ago about the parallels with game theory and theory of interacting many-particle systems in physics. If one starts from a game theory context/background the postulate that the motion of particles is governed by rules that would guarantee minimization (or maximization) a global function, like energy or action, may seem a bit peculiar. Since in non-cooperative game theory every agent is supposed to attempt to maximize its own utility.

Would it be possible to derive the equations of motion of particles in an interacting  system without the need to first postulate the existence of such a global function?  I.e. that minimization of energy, or action, is an emerging behaviour of a many-particle system (e.g. an electron gas) rather than a property that is already built-in to the theory through a postulate.

 

The idea is to replace the strong assumption of the existence of a global function by a much weaker assumption that each particle's movements are governed by  "local optimization" rules. Nevertheless, the execution of these local rules by each particle would result in a global minimum to be achieved.

 

Looking again into game theory, one way this could be achieved is if we could assume that particles have some form of memory  that guides them to equilibrium solutions through repeated games.

This may require that particles (e.g. electrons) have some internal degrees of freedom (states) that can act as memory storage.

 

 

 

 

 

BBC's Click on the future of wireless devices in homes



BBC's  technology program Click on 3 April 2013  looks at new developments in WiFi technology and its impact on networks and devices around the home.  It is mainly focusing on 802.11ac  and WiGig  but also briefly examines issues related to congestion and coexistence in 2.4 GHz band.

Here is the link to the program,  where I contributed with advice and some commentary:

http://www.bbc.co.uk/iplayer/episode/b01rswmy/Click_30_03_2013/

and here in the link to the  Persian version

http://www.bbc.co.uk/persian/tvandradio/2013/04/130412_click_673_wireless.shtml

Connections between game theory and interacting many-particle systems

I have been "flirting" with game theory on and off since a few years but only recently have started to grasp some of its fundamental ideas, and appreciate its importance

Having come from a background in quantum and classical many-interacting systems, right from the begin I couldn't help but wonder about if there are links (or even deep connections) between game theory, essentially a theory of interactive decision making, and theory of many-particle systems.

Taking a classical systems where particles interact through conservative forces  as example:
-each particle can be considered as player
 the set of actions for each particle (player) are its position and velocity (the action space is continuous)

-the utility of each particle is the sum of its kinetic and potential energy

-players are engaged in a game of sequential moves



-in each move a particle chooses the action that minimizes its energy

I think this rules would  result in the conventional molecular dynamics

For quantum systems, one interesting aspect (I think) is that  particles action space is their positions {r_1, ... r_N} and the strategies are mixed strategies, with \psi* \psi, being the joint probability distribution that particle 1 selects action r_1, particle 2 selects action r_2, particle N selects action r_N.

One interesting observation is that in "physical"  systems the laws of motion, i.e. how a particle selects its next move, are derived by minimizing a global function, i.e the systems Lagrangian, i.e. somehow it is hypnotized that all particle would move in away that would result in minimization of the global function. On the other hand, in "non-cooperative game  theory each player is attempting  to maximize its own utility, and generally there is not a notion of a global function. Only in especial cases, like potential games (I believe) utility optimization by selfish players  result in optimization of a global function.

Perhaps interestingly one might pose the question, why in the case of physical systems the general rule seems to be   that the rules obeyed by individual  particles should be derived by hypothesizing  global minimization. 


Other interesting avenues to explore are if notions such as mean-field solutions, or even Walter Kohn's  Density Functional Theory  have analogies in many-player game theories.  

 

 

Upcoming/recent events and presentations

-LTE Strategies, London, 5-7 November 2012
  http://www.ltestrategies.com/Event.aspx?id=706436


-IEEE DySPAN 2012, Policy Panel (with Santosh Kawade), Bellevue,  16-19 October,
 Washington,  USA
  http://www.ict-acropolis.eu/index.php?option=com_content&view=article&id=166&Itemid=78

-ICT Acropolis/WinnCom-Europe Industry Panel, Brussels, 27 June 2012
 Slides and Video available from: 
 http://www.ict-acropolis.eu/index.php?option=com_content&view=article&id=166&Itemid=78 

IET symposium on cognitive radio and white space technologies

The first IET symposium on cognitive radio and white space technologies was held last June in the historical Savoy Place in London.

This was a very useful event for anyone that wanted to  find out about the latest in  regulatory and industry developments in white space technology, especially in the UK.

  

The video of my presenttaion "Cognitive Radio Access to TV White Spaces: A Stepping Stone Towarads Intelligent Spectrum Sharing" is now available to watch from:

http://scpro.streamuk.com/uk/player/Default.aspx?wid=14072&ptid=32&t=0

Slides from all  presentations are also available from

 http://conferences.theiet.org/tvws/presentations/2012/index.cfm