School notes

Learning Stimulus Module (LSM)

2008-03-01T14:29:00.000-08:00

I was discussing the idea of a periodized training plan for a cognitive radio with a friend the other day. He had suggested that during low traffic times, such as late at night, it might be a good idea for the cognitive radio to go into high learning mode.

This mode would require more resources which would take away from the main end goal of performance, but because it was a lot priority time the effect on performance wouldn't be as much of an issue. The problem with this logic is that in order for the radio to learn it is going to need inputs in order to develop a history of cases from which to refer to for future learning. During a low traffic period such as late at night there is less traffic in the over all spectrum environment and there for less of a chance to take in inputs from which to develop decisions which in turn build up the case based library.

He had a great idea to create an artificial stimulus which could create inputs for the system. These inputs would simultate things such as other radios operating in the same spectrum. The cogntive node would not know that this is actually an artificial stimulus and would follow along its learning path of reading the meters, making a decision based on a policy tree and case based reasoning flow chart. These decisions contribute to the overall case library.

This learning stimulus would engage during low period times which is an efficient use of the radio. While it might typically lay dormant during these times of low traffic with the use of the LSM it can train itself without affecting the end goal of overall performance. The LSM can shut down when the radio needs to send priority information, or when there is real spectrum stimulus in the area.

Soar Cognitive Engine

2008-02-27T17:46:00.000-08:00

There was a paper included in this week's class readings that discussed Applications of Machine Learning to Cogntive Radio

It was an interesting paper and dealt mainly with fundamental ideas about learning, reasoning as they can be applied to cognitive radio. However at the very end of the paper they mentioned a real implementation of the ideas by using an Ossie Software defined radio and the Soar Cognitive Radio Engine.

There is a little bit more detail of their implementation here.

I am in the process of learning more about this Soar Cognitive engine. It is a general computational model that is geared towards a Unified Theory of Cognition. Not that I know what that means yet. It seems to have found application in many different fields from psychology to AI in video games and most notably for me Cognitive radio.

This could be an a good avenue to explore for research given the little bit of work using it in a cognitive radio framework?

I saw that an MS student did a thesis on using the OSSIE SCA to develop a software defined 802.16 system.

I wonder if this implementation could be adapted with the Soar cognitive engine to develop a cognitive WiMAX system? It looks like it's doable since the above papers have followed a similar approach of synergy between OSSIE and Soar. It would still be novel because it is a WiMAX implementation.

2008-02-26T10:45:00.000-08:00

Just some initial thoughts on research project

Cognitive WiMAX
Justifications
Enable cost effective deployments
Minimize need for expensive System Integrators
Enable less skilled labor to install
Self starting / Autonomous initialization
Important for DOTs and large scale deployments
Important for rural and developing/3rd world nations
Fast deployments for emergency and hostile environments
Account for changes and crowding of spectrum
Cost effective long term operations
Minimize requirement for in-field service
Capability to adapt to changing wireless landscape

Justifications
SDR based radios vs System on Chip
Higher return on initial investment
Lifespan of 15-20 years instead of 3-5 years based on how fast technology improves
Lower cost installation and maintenance
Synergy with the way a DOT or government does business
One time high dollar amount procurements w/o budget for upgrade/maintenance
Improved Performance
Make better use of available spectrum
Optimize configuration based on existing conditions improve overall throughput/performance

General Concept
Some Ideas
Spectrum Decision Methodology
User requirements  System knobs
Data rate
Acceptable error rate
Delay bound
Transmission mode
Bandwidth requirements
Carrier frequency

Adapting WiMAX transport protocols to a dynamic spectrum environment

Ideas (cont)
Handover Delay
Delay caused by spectrum handoff
Contrast to delay caused by mobile handoff
Synergy with my current work with Cisco quantifying handoff delay between APs from a mobile client
Co-existence of WiMAX with other WiMAX and 802.11 in unlicensed bands
How the scheduled MAC of WiMAX interoperates with a CSMA/CD based systems like 802.11
Adapting Sports Physiology Models to ‘training’ a CR
In Sports Physiology there is a concept known as Periodized Training
Variables such as Training volume and Training intensity are manipulated throughout the year in order to optimize performance at a specific time such as for the competition phase or a specific event as the finals

Research
Develop a ‘training’ plan for a CR radio node
Adapt physiological models of periodized training to CR
Develop schedule for ‘when’ a CR should be in a certain mode of operation in order to optimize the performance during certain events.
Similar to taking an athlete and training them for a competition season or a specific event
Matveyev’s Model of Periodization

For example
In the prepatory phase, a CR would be in a spectrum sensing mode
Power usage HIGH
Cooperative with other nodes higher overhead
LOW throughput  lower performance
In the ‘competition’ or high performance phase
Lower sensing , lower cooperation,  more resources for throughput higher performance
The CR knowingly sacrifices performance during non-mission critical times in order to learn more which in the end should optimize the end goals when needed for higher priority data

definitions

2008-02-07T18:00:00.000-08:00

Lots and lots of definitions of cognitiv radio.

I like James Neel's definition from this presentation:
A cognitive radio is a radio whose control processes
permit the radio to leverage situational knowledge
and intelligent processing to autonomously adapt
towards some goal.

Cognitive WiMAX vs typical cognitive radio

2008-02-07T17:40:00.000-08:00

Most of the emphasis on cognitive radio is for a secondary user to operate in the same spectrum as a primary user. So there is a lot of focus on dynamic spectrum access and the ability to sense the presence (and modulation code) of a primary user and then vacate the channel.

But with WiMAX MAC is built around a scheduler. Where a base stations schedules packest to users so there is no need for carrier sense and collision detection. The goal was a higher quality of service. But with this dedicated nature of base station to subscriber there is not as much emphasis on searching for a primary user, because teh WiMAX is the primary user.

There is more opportunity to use cogntive abilities to optimize the quality and throughput between endpoints. For example, just like 802.11 based systems, WiMAX will scale up or down the bandwidth depending on how far away the receiving radio is. Closer together--> higher signal--> controller sets a higher bandwidth modulation.

"system would use cognitive radio technology to identify interference and poor links and then change its own signal transmission to improve the weak links." taken from here

So the only factor here is proximity. If more information was used to make the decision such as Bit error rate, snr... a better decision can be made.

A more driving force behind a cogntive WiMAX would be self initialization for easy deployment/startup and long term operations for emergency and 3rd world countries.

There is some effor in 802.16h for interoperation in unlicesened bands but that is different than a complete cognitive function.

Random cogntive radio research ideas

2008-02-07T07:33:00.000-08:00

I read a great paper that outlined several potential research issues with cognitive radios:
[1] I. F. Akyildiz, W.-Y. Lee, M. C. Vuran, and S. MOhanty, \NeXt generation/dynamic access/cognitive radio wireless networks: A survey," Elsevier Computer Networks Journal, vol. 50, pp. 2127{2159, September 2006.

1) Latency caused by spectrum handoff
-In the work I've been doing lately with mobile roaming we have been quantifying the latency delay created during a handover between a mobile node and a roadside accesspoint. This delay can be instrumental in causing issues with applications such as video.

A research idea would focus on the latency delay that would be incurred with a cogntive radio when it decides to switch spectrums. Just like with a layer 2 handoff there is going to be some latency when the radio and it's partner or network decides to vacate spectrum and move to a new allocation.

2)Identifying spetrum bands based on combining many characteristics and not just if the spectrum is available or not
-capacity (which is affected by interference level and path loss)
-delay
-link error rate
-holding time
==> selecting the appropriate spectrum for the particular application

3)Spectrum decision.
What are the factors that go into makin a decision in which spectrum to switch to.
-User requirements drive this decision
-data rate
-acceptable error rate
-delay bound
-transmission mode
-bandwidth requirements

4) routing algorithms in an open spectrum enviroment.
-Routing has never had to think about open spectrum environments This adds a new dimension to routing protocols and how they are inter related to spectrum management

5) Transport protocols for xG networks
TCP/UDP for dynamic specturm environments and cooperation with upper and lower layers. Again same as above issue, current transport protocols have not had to consider this issue in the past.

6) Spectrum sensingin OFDM based networks. OFDM seems to be the darling for cogntive radio applications. And sensing i guess can be performed quickly but it is complex, but because there are a large # of carriers the sensing algorithms need to be optimized so the # of samples needed to detect primary users is minimzed within a given detection error probablity.

7) just a conceptual idea about combining Remote Wireless Sensor networks with a cognitive radio network. Sort of pie in the sky and maybe not viable. By nature a RWSN is going to be cheap and easily deployable, low power. stand alone. In contrast a cogntive radio is more complex. Can you tie the two together. What about building a very cheap energy detetctor for a particular block of spectrum. In fact build 10 different ones to cover a range of spectrum and put them on their own RWSN mote. Deploy them around a CR node. Let the motes perform the sensing and send that information to the CR node.

Rapid Deployment and Maintenance Free operation of Wireless infrastructure

2008-01-19T07:31:00.000-08:00

This is a potential idea for a dissertation. One of the biggest cost factors for a large scale deployment of a wireless system isn't really the hardware itself. The hard infrastructure (cabinets, poles, grounding, pads) etc. costs a lot as well. But I think the biggest cost is the systems integrator costs for design, installation, and long term maintenace.

The design and deployment is complicated enough that you'd need a batch of highly skilled technical people to get them out there. One unforseen change in spectrum usage from a random noise signal and it will have to be changed. Again, call out the Masters educated techs and fix it.

A cognitive radio based wireless infrastructure would be able to adapt to changes in the wireless environment, and be easily deployed. It wouldn't take a highly skilled person to tack them up on a pole and run wires to them.

The DOT is in a position right now where their maintenance forces are severely taxed just for the basic infrastructure such as signals. Their workforce is untrained in basic IP based devices such as cameras and wireless radios. So in order to maintain it themseleves they will have to 1) educate their workforce and 2) increase their workforce. Right now it seems that they don't want to do either and are even going in the opposite direction in terms of downscaling and privatizing maintenance functions.

but that privitazation is going to increases costs significantly especially when you have a technical product and complex function as a wirelss infrastructre.

A cognitive based system would be require a variet of PHY, MAC and routing options This might be a good dissertation topic. In addition to a cognitive radio aspect I think there is a large need for a cogntive network aspect. In the MacKenzie, Da Silva paper on cognitive networks they mention
"For instance a particular MAC protocol may optimize for power consumption, creating higher hop count routes that use short links. Howeer this mode of operation might result in additional end-to-end delay (due to the additional processing, queing and transmission delay that goes along with higher hop count routes) which in turn could affect the transport layer leading to more transmissions

I've seen first hand how higher hop counts lead to decreased throughput. So this issue is very important. A single cognitive radio might have it's own selfish requirements that will help it's overall goal but an overriding umbrella of a cognitive network with emphasis on a systems end-to-end goal is going to take each radio's decisions into account and make the best overall change to the system operation.

Cross Layer optimization is going to be important

2007-11-30T08:50:00.001-08:00

Cross Layer Optimization
link 1
link 2

This concept is going to be important from the perspective of developing a cognitive and adaptive WiMAX radio. The use of MIMO and other advanced antenna technologies are going to enhance the PHY layer significnatly. From a simulation perspective a cross layer approach is going to be required in order really show the true performance. the MAC layer side of the system needs to be incorporated with the advanced PHY layer.

There is research in the area of developing better simulations in order ot address the cross layer issues.

Definitely need to consider some of this with regards to cognitive WiMAX

ITU- United Nations approval of WiMAX

2007-11-14T18:30:00.001-08:00

ITU approval

good mobile wimax article

2007-11-14T18:26:00.001-08:00

Microwaves RF mag article

dedicated pilots / MIMO WiMAX beamforming

2007-11-14T18:22:00.000-08:00

http://www.home.agilent.com/agilent/editorial.jspx?action=download&cc=US&lc=eng&ckey=1213544&nid=-536902344.536910932.00&id=1213544

WiMAX plug fest architecture/test plan

2007-11-14T18:21:00.000-08:00

http://www.wimaxforum.org/technology/downloads/2nd_Mobile_WiMAX_PlugFest_White_Paper.pdf

Cisco buys into WMAX

2007-11-14T18:20:00.000-08:00

http://www.unstrung.com/document.asp?doc_id=66951

knobs for cognitive radio

2007-11-13T09:35:00.000-08:00

Radio paramters
transmitter power, frequency, bandwidth, modulation, and channel
coding

FroM Rieser PhD Thesis

0 Power
1 Carrier Frequency (Fc)
2 Bandwidth
3 Symbol Rate
4 Modulation
5 Forward Error Correction (FEC)
6 Payload/frame length
7 Automatic Repeat Request (ARQ)
8 Dynamic Range
9 Equalization
10 Encryption
11 Antenna Configuration
12 Voice
13 Noise Cancellation (limiting)
14 Interference Temperature
15 Time Division Duplex (TDD)

cognitive 802.16 poster from 2007 Wireless@vt workshop

2007-11-11T17:10:00.001-08:00

Poster

Conflict between 802.16h and 802.22

2007-11-11T16:59:00.000-08:00

802.16h was originally intended for coexistence of WiMAX in unlicensed bands.
see article at wifi planet detailing some of the tension between 802.16h and 802.22

They ammended the scope of the PAR to include coexistence with primary users. in addition to the coexistence with self. This is a huge issue as it directly places 802.16h in tension with 802.22. This places overlap in their scopes. If 802.16h can expand into the TV bands then 802.16h is essentially the same thing as 802.22

This letter shows the response from 802.16h to a letter from 802.22 about overlap in their scopes.

Periodization from Sports Physiology applied to cognitive radio

2007-11-11T13:23:00.001-08:00

In perodized training, the phsyical development is broken down into specific periods. Each period builds on the last period and leads into the next one. The ultimate goal is to be that fittest for the most important races. This means that during the earlier periods, peformance will be degraded in order to develop fitness. Performance is sacrificed in the earlier periods so that they will be in the best condition during the racing period.

How can this be applied to cognitive radio.

Develop specific periods. In some periods actual performance is not very good. But congitive abilites are higher. Sacrifice performance in order to learn more about the current environment. While learning the radio can't perform as well as it could, but it is developing the ability to perform better latter on.

Later on, switch to a new period where performance is maximized. In this period the radios cognitive abilities are somewhat dimished in order to increase it's ability to perform.

For example, if there is no important data to send at the moment switch to a low performance/high cognitive period. Higher overhead and lower performance but is ina learning state where the knowledge gained can be of use when needed.

When higher priority data is required switch to a new phase of operation.

So rather than be in the same state all the time, change operation modes in order to maximize capabilities when they are needed

articles
one
wiki

WiMAX applications to transportaion

2007-11-11T13:18:00.000-08:00

Pt-to Pt and/or Pt to Multipoint links to support ITS devices in the field
-Sensors
-DMS
-Cameras, IP video
- VOIP to field personnel
- construction monitoring
- infrastructure monitoring
- any other ITS requiring comm
-higher bandwidth backhaul for local DSRC

DOTS looking into it
SCDOT
PENN DOT
AZ DOT
NY DOT
FL DOT

Long range, potential NLOS capabilities
high quality of service that lends itself to applciaitons such as video. Scheduled Downlink/uplinks and not CSMA

Mobile WiMAX, vehicle to roadside
-vehicle to vehicle comme through a base station
-VII applications, Weather sensing using information from individual vehicles

Coexistence issues between DSRC and WiMAX
potentially similar spectrum
QOS for multimedia delivery

Deployment scenarios for a DOT
-camera specific / ITS designs
License requirements
-4.9 usage for public safety

802.22 vs Cognitive WiMAX

2007-11-11T13:13:00.000-08:00

802.22 is planning on using an OFDM structure similar to 802.16. 802.22 is being designed specifically as a cognitive technology due to the requirement of coexistence between units and the need to not interfere with incumbents (television, wireless microphones)

Besides the frequency being used, what would the difference be between a fully cognitive 802.16 and 802.22. I guess the requirement to not defer to an incumbent

thoughts on coexistance cognitive WiMAX

2007-11-11T13:00:00.000-08:00

802.16h focused only on coexistence of WiMAX in the unlicensed bands. It is not really a fully cognitive application.

Berleman paper talked about techiques for how 802.16 can block out competing 802.11 radios in the same spectrum. Because of 802.11's reliance on listen-before-talk MAC the WiMAX is able to block out 802.11 as needed by making it's tranmissions longer than the contention period for 802.11. This in effect does not allow the 802.11 to transmit when the 802.16 wants to. Of course this is a totally unfair type of methodology.

Possible similarilty between 802.16 coexistence and 802.11e in terms o fthe hybrid controller and sharing a single frequency channel in the time domain.

802.22 will use coexistence beacons to help with self coexistence of multiple Base Stations in the same area.
-Coexistence beacons will be time stamped, CPE from neighboring networks may be able to overhear the beacons. They will be looking for them to be able to help inform their own basestations of potential hidden nodes that the base might not be able to see

Currently a WimAX deployment requires significant planning for frequency reuse strategies. The Base station coordiantion of large scale deployments is similar to cell phone type deployments. While this is an acceptable and almost required deployment strategy for North America what about in highly rural and depressed 3rd world countries. Or in areas where countries are bordering with each other.

It is highly unlikely that you are going to be able to enable such a strong coordination between base stations. More likely is that you are going to have people just setting these up without knowledge of the other Base stations in the area. Licenses may be granted for a particular area by a country but these will be invalid when you are on the border of another country.

Cognitive WiMAX would lend itself to an automated initialization sequence upon powering up. This enables a low level of skill to be required for the design and deployment of a network which lends itself to a 3rd world type deployment. A base station and accompanying CPEs would be able to start up and sense the environment in terms of frequency availability and potential interference. based on this knowledge it can change it's PHY setup to accomadate the current environment.

Question, if a Base station is constantly sensing and decides to change frequencies than it will have to tell all the CPEs but what happens if a new CPE turns on but doesn't know what frequency the Base is on. In current WiMAX the frequency is fixed and the CPE knows where it needs to be to find the base station. In this type of case, the CPE is going to have to go through a search mechanism for scanning the potential frequencies that a base station would be on until it finds it.

Current WiMAX is a narrow profile compared to what the 802.16 standard is capable. This was required to develop synergy among vendors and to solidify a development plan and create more economy of scale for the development of WiMAX.

A cognitive WiMAX would be a very flexible radio, capable of changing its frequency, power and range, and other variables to accomadate the desired operation and the wireless ecosystem in its surrounding area.

The 802.16 MAC structure has an inherent weakness in that it is based of a scheduling system coordinate by the base station. there is no listen than talk of like 802.11. The WiMAX will provide higher quality of service and more efficient bandwidth but if there is enough noise or interference to block the preamble and the DL/UL scheduling there might be problems.

frame based 802.16 MAC requires significant rigourous protection

Study plan for understanding WiMAX

2007-11-11T12:45:00.000-08:00

OFDM
-Frame structure
-preamble, FCH, DL, UL Mapping

OFDMA

QOS definitions
-Service flows
-UGS
-rPTS
-ErPTS
nrtPS
BE

MAC scheduling

TDD vs FDD
TDD is currently preferred, all WiMAX profiles right now are using TDD, all the mobile allplications will use TDD

Fast Feedback
UL ranging

AMC
Cyclic prefix

HARQ vs ARQ

Modulations Schemes
-QPSK
-16 QAM
- 64QAM

Convultoin Code (CC) vs Convultion Turbo Code (CTC)

Block Turbo Code

Low density Parity Check

MAC Layer fundamentals
-Docsis cable modem standard

Mobility/Handoff schemese
-Hard Handoff HHO
-Fast Base station Switching (FBSS)
-Macro Diversity Handoff

-Security
-EAP
- AES, CMAC
-3 way handshake

Smart Antennas
-Beam forming
-STC
-Spatial Multiplexing
-MIMO
-Alamouti STC, USM
-Collaborative SM

Frequency Reuse techniques

-Multicast Broadcast service

-MAP
-Media Access Protcol
-Cyclic Shif Transmit Diversity

CDF

Submap Burst structures

1xEVDV evaluation methodology

Definition of spectral Efficiency

Standards Evolution
Phy / MAC development at IEEE level vs WiMAX profile

WiMAX Network Reference Model (NRM
-MS, ASn, CSN

Reality, Relevance of WiMAX
-Last mile solution
-MANd
Intel's push
-low cost CPE

Momentum of WiMAX forum
-similar model, historic path of WiFI

Global / Rural implications
-Broadband to 3rd world
rural broadband to VA and other parts of USA

Fixed WiMAX vs other fixed backhaul solutions
Mobile WiMAX vs 3 G cellular

vs future technologies 802.22, 802.20