Cognitive radio network enabling new wireless broadband opportunities
Download
1 / 30

Cognitive Radio Network: Enabling New Wireless Broadband Opportunities - PowerPoint PPT Presentation


  • 429 Views
  • Uploaded on

Cognitive Radio Network: Enabling New Wireless Broadband Opportunities. Cavalcanti, D. and Ghosh, M. Cognitive Radio Oriented Wireless Networks and Communications, 2008. (CrownComm 2008) Lecturer: Chang Han-Tien. Outline. Introduction Regulatory Scenario Overview of The 802.22 Standard

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'Cognitive Radio Network: Enabling New Wireless Broadband Opportunities' - daniel_millan


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
Cognitive radio network enabling new wireless broadband opportunities l.jpg

Cognitive Radio Network: Enabling New Wireless Broadband Opportunities

Cavalcanti, D. and Ghosh, M. Cognitive Radio Oriented Wireless Networks and Communications, 2008. (CrownComm 2008)

Lecturer: Chang Han-Tien

Cognitive Radio Network: Enabling New Wireless Broadband Opportunities


Outline l.jpg
Outline Opportunities

  • Introduction

  • Regulatory Scenario

  • Overview of The 802.22 Standard

  • Spectrum Management Model

  • Conclusions

  • Comments

Cognitive Radio Network: Enabling New Wireless Broadband Opportunities


Introduction l.jpg
Introduction Opportunities

  • Last-mile broadband access

    • different solutions may be more efficient for different applications and deployment regions

  • A successful deployment of wireless broadband in rural communities should consider

    • Coverage, Capacity, Installation and operational costs, Business models

  • WiFi network (IEEE 802.11)

    • design for short/medium range connectivity

    • solution for long-distance access [2]

  • Cellular system

    • the deployment cost is an issue for rural communities.

Cognitive Radio Network: Enabling New Wireless Broadband Opportunities


Introduction cont d l.jpg
Introduction (cont’d) Opportunities

  • Cognitive Radio [4]

    • an intelligent wireless communication system that is aware of its environment (sensing spectrum)

    • uses the methodology of understanding-by-building to learn from the environment

    • adapt to statistical variations in the input stimuli

  • Two objectives

    • highly reliable communication whenever and wherever needed

    • efficient utilization of the radio spectrum

Cognitive Radio Network: Enabling New Wireless Broadband Opportunities


Introduction cont d5 l.jpg
Introduction (cont’d) Opportunities

  • IEEE 802.22 (WRANs)

    • operate in the TV spectrum band (54 MHz~862 MHz) as secondary users

    • under regulatory rules to avoid interference with the primary users (incumbent, TV broadcasting)

  • Key issues

    • Incumbent protection

    • Self-coexistence

    • Spectrum management

Cognitive Radio Network: Enabling New Wireless Broadband Opportunities


Regulatory scenario l.jpg
Regulatory Scenario Opportunities

  • Cognitive radio networks

    • enable flexible, efficient and reliable spectrum

    • by adapting the radio’s operation characteristics to the real-time conditions of the environment

    • limited applicability under legacy spectrum usage

      • Command and control

      • Exclusive-use

    • New dynamic spectrum access models

      • In order to exploit the full capabilities of CRNs

Cognitive Radio Network: Enabling New Wireless Broadband Opportunities


Regulatory scenario cont d dynamic spectrum access models l.jpg
Regulatory Scenario (cont’d) OpportunitiesDynamic spectrum access models

  • Shared-use of primary licensed spectrum

    • where secondary users share the spectrum with primary users on a non-interfering basis

    • Spectrum underlay

      • Limit the secondary users’ transmit power to very low level in order not to interfere with primary users

    • Spectrum overlay

      • Enable devices to operate in the spectrum white spaces

      • Implement reliable incumbent detection and frequency agility mechanisms

Cognitive Radio Network: Enabling New Wireless Broadband Opportunities


Regulatory scenario cont d dynamic spectrum access models8 l.jpg
Regulatory Scenario (cont’d) OpportunitiesDynamic spectrum access models

  • Spectrum commons

    • the spectrum is shared under equal rights by all devices on an unlicensed basis in the model

    • Open-access model in ISM (2.4GHz) and I-NII (5 GHz)

    • Reduce the overcrowding condition in these unlicensed bands

  • IEEE 802.22 standard

    • shared-use spectrum model

    • protection of primary users while providing Quality of Service (QoS) for the secondary users.

Cognitive Radio Network: Enabling New Wireless Broadband Opportunities


Regulatory scenario cont d protection of incumbents l.jpg
Regulatory Scenario (cont’d) OpportunitiesProtection of Incumbents

  • Spectrum sensing is a key technology to detect incumbents in the TV bands.

  • Incumbent Detection Thresholds (IDT)

    • If an incumbent signal above the IDT is detected, the secondary system must react appropriately to avoid harmful interference.

    • The incumbent signal shall be detected with probability exceeding the Probability of Detection (PD) parameter

    • Probability of false alarm shall be equal or lower the the PFA parameter

    • Channel Detection Time (CDT)

Cognitive Radio Network: Enabling New Wireless Broadband Opportunities


Regulatory scenario cont d protection of incumbents10 l.jpg
Regulatory Scenario (cont’d) OpportunitiesProtection of Incumbents

  • If an incumbent signal above the IDT

    • In the adjacent channels

      • apply transmit power control to avoid leakage in other channels

    • In the operating channel

      • vacate the channel within the Channel Move Time (CMT)

      • an aggregate transmission time equal to the Channel Closing Transmission Time when switch to backup channel

Cognitive Radio Network: Enabling New Wireless Broadband Opportunities


Regulatory scenario cont d protection of incumbents11 l.jpg
Regulatory Scenario (cont’d) OpportunitiesProtection of Incumbents

  • PFA is important for the secondary systems’ QoS and efficient spectrum utilization [13]

Cognitive Radio Network: Enabling New Wireless Broadband Opportunities


Overview of the 802 22 standard l.jpg
Overview of the 802.22 standard Opportunities

  • 802.22 WRAN is a point-to-multipoint system

    • Base station (BS)

    • Consumer Premise Equipments (CPEs)

      • equipped with a spectrum sensing module

      • meet the regulatory requirement of sensing

    • Expected coverage area is around 30 Km

    • Address markets in sparse populated areas

Cognitive Radio Network: Enabling New Wireless Broadband Opportunities


Overview of the 802 22 standard cont d the 802 22 phy l.jpg
Overview of the 802.22 standard (cont’d) OpportunitiesThe 802.22 PHY

  • OFDMA multiple access

  • Data rate

    • 1.5 Mbit/s in the downstream (DS)

    • 384 Kbit/s in the upstream (US)

  • Support 255 CPEs per BS per TV channel (6MHz)

Cognitive Radio Network: Enabling New Wireless Broadband Opportunities


Overview of the 802 22 standard cont d the 802 22 mac l.jpg
Overview of the 802.22 standard (cont’d) OpportunitiesThe 802.22 MAC

  • BS controls the access to wireless medium

    • take on-demand basis in the US direction

    • use TDM (Time Division Multiplexing) in the DS

  • New range of cognitive radio feature supports

    • Reliable incumbent detection

    • Frequency agility

    • Self-coexistence

      • the coexistence amongst 802.22 WRANs

Cognitive Radio Network: Enabling New Wireless Broadband Opportunities


Overview of the 802 22 standard the 802 22 mac cont d superframe and frame structures l.jpg
Overview of the 802.22 standard - The 802.22 MAC Opportunities(cont’d)Superframe and frame structures

  • Superframe consists of 16 frames

    • facilitate incumbent protection, synchronization, and self-coexistence

    • start with the superframe preamble, frame preamble, Superframe Control Header (SCH), and Frame Control Header (FCH)

Cognitive Radio Network: Enabling New Wireless Broadband Opportunities


Overview of the 802 22 standard the 802 22 mac cont d superframe and frame structures16 l.jpg
Overview of the 802.22 standard - The 802.22 MAC Opportunities(cont’d)Superframe and frame structures

  • Frame is divided into DS and US sub-frames

  • DS/US MAPs and channel descriptor broadcast messages (DCD and UCD)

  • Option in the US sub-frame

    • be used for ranging, bandwidth request and Urgent Coexistence Situation (UCS) notification

  • Self-Coexistence Window (SCW)

    • For coexistence beacon transmissions at the end of US sub-frame

Cognitive Radio Network: Enabling New Wireless Broadband Opportunities



Overview of the 802 22 standard the 802 22 mac cont d incumbent detection support l.jpg
Overview of the 802.22 standard - The 802.22 MAC Opportunities(cont’d)Incumbent Detection Support

  • Scheduling of network quiet periods (QPs)

    • avoid overlapping of data transmissions

    • BS schedules network QPs for sensing

    • suspend all the traffic in the cell, let CPEs sample the channel for detecting the incumbent

    • intra-frame and inter-frame quiet periods

    • minimize the impact of QPs on users’ QoS

Cognitive Radio Network: Enabling New Wireless Broadband Opportunities


Overview of the 802 22 standard the 802 22 mac cont d incumbent detection support19 l.jpg
Overview of the 802.22 standard - The 802.22 MAC Opportunities(cont’d)Incumbent Detection Support

  • Channel measurement management

    • In-band (i.e. in the operating channel and first adjacent channels)

      • scheduled by the BS during the QPs

    • Out-of-band (other channels that may be used as backup

      • may be done during the CPEs idle time

      • Occupied by other WRANs, should use the QPs schedule

Cognitive Radio Network: Enabling New Wireless Broadband Opportunities


Overview of the 802 22 standard the 802 22 mac cont d incumbent detection support20 l.jpg
Overview of the 802.22 standard - The 802.22 MAC Opportunities(cont’d)Incumbent Detection Support

  • Notification phase

    • advertising the QP scheduling in the SCH

    • channel quiet request message (CHQ-REQ) to stop traffic within its cell

    • bulk measurement request message (BLM-REQ) to request CPEs to perform measurements

    • the result are reported back in bulk measurement reply message (BLM-REP)

Cognitive Radio Network: Enabling New Wireless Broadband Opportunities


Overview of the 802 22 standard the 802 22 mac cont d incumbent detection support21 l.jpg
Overview of the 802.22 standard - The 802.22 MAC Opportunities(cont’d)Incumbent Detection Support

  • a CPE detected the presence of incumbent

    • use the UCS notification slots to inform BS

    • the notification transmitted using a contention-based or CDMA-based

    • BS combines the information from various CPEs

    • React more efficiently in timely manner

Cognitive Radio Network: Enabling New Wireless Broadband Opportunities


Overview of the 802 22 standard the 802 22 mac cont d frequency agility l.jpg
Overview of the 802.22 standard - The 802.22 MAC Opportunities(cont’d)Frequency Agility

  • An incumbent is detected on the operating channel (N) or adjacent channels (N-1,N+1)

  • BS triggers a switch to a backup channel

  • Maintain a list of back channels

  • Challenge: a seamless channel transition

  • Two channel management mode

    • Implicit mode (DCD Broadcast message)

      • Don’t require extra management messages

    • Explicit mode (CHS-REQ, Channel switch request)

      • Provides greater flexibility in different granularities

      • To single CPE or to a group of CPEs (multicast message)

Cognitive Radio Network: Enabling New Wireless Broadband Opportunities


Overview of the 802 22 standard the 802 22 mac cont d self coexistence l.jpg
Overview of the 802.22 standard - The 802.22 MAC Opportunities(cont’d)Self-coexistence

  • Synchronize the QPs among neighboring cells, in order to reduce the overall QPs

    • Synchronize the superframes using positioning satellite capabilities at the BSs

    • Exchange their QP schedule through the SCH as well as the Coexistence Beacon Protocol

    • use SCW to allow CPEs (BSs) to exchange coexistence beacons (QP schedule’s information)

  • Each BS should select CPEs to transmit CBP packets according a periodic schedule, and it should also select CPEs to listen for CBP packets

Cognitive Radio Network: Enabling New Wireless Broadband Opportunities


Overview of the 802 22 standard the 802 22 mac cont d self coexistence24 l.jpg
Overview of the 802.22 standard - The 802.22 MAC Opportunities(cont’d)Self-coexistence

  • When a CPE receives a CBP packet from a neighboring cell

    • Forward to the information to its BS

    • Exchange information amongst neighboring cells

  • Efficient spectrum sharing

    • Using the intelligent scheduling mechanism

    • Dynamic resource renting/offering

    • On-demand spectrum contention

Cognitive Radio Network: Enabling New Wireless Broadband Opportunities


Spectrum management model l.jpg
Spectrum Management Model Opportunities

  • Spectrum Manager

    • a central entity collocated with the WRAN BS

    • taking the key decisions and triggering the proper events/actions (central intelligence)

    • a part of the MAC layer management entity

  • Spectrum Automaton

    • act as a slave to the SM

    • control the local CPE’s spectrum sensing function as requested by the BS’s SM

Cognitive Radio Network: Enabling New Wireless Broadband Opportunities


Spectrum management model cont d l.jpg
Spectrum Management Model (cont’d) Opportunities

  • Spectrum Manager’s main functions

    • 1. Maintain spectrum availability information;

    • 2. Channel classification and selection;

    • 3. Association control;

    • 4. Trigger frequency agility related actions;

    • 5. Manage mechanisms for self-coexistence.

  • Geo-location module

    • acquire precise positioning and time synchronization information

Cognitive Radio Network: Enabling New Wireless Broadband Opportunities


Spectrum management model cont d27 l.jpg
Spectrum Management Model (cont’d) Opportunities

Cognitive Radio Network: Enabling New Wireless Broadband Opportunities


Overview of the 802 22 standard the 802 22 mac cont d superframe and frame structures28 l.jpg
Overview of the 802.22 standard - The 802.22 MAC Opportunities(cont’d)Superframe and frame structures

  • Collaborative spectrum sensing and incumbent database

    • Aggregating information from other sources

    • Make decisions based on spectrum sensing information only when the incumbent database isn’t available

  • Frequency agility actions

    • Switch the entire cell to a new operating channel;

    • Direct a single CPE or a group of CPEs to a different operating channel;

    • Terminate operation in a given channel for a single CPE, a group of CPEs or the entire cell;

    • Inform CPEs of channels status updates

Cognitive Radio Network: Enabling New Wireless Broadband Opportunities


Conclusions l.jpg
Conclusions Opportunities

  • The shared usage model with primary users can be realized with existing cognitive radio technologies

  • Enable new opportunities for wireless broadband access

  • Protection of incumbents and achieve efficient spectrum utilization

  • Future work

    • Optimized scheduling algorithms

    • Channel selection and intelligent scheduling algorithm

    • Collaborative sensing techniques

    • System level evaluation to assess the robustness of 802.22

Cognitive Radio Network: Enabling New Wireless Broadband Opportunities


Comments l.jpg
Comments Opportunities

  • It’ important to find the balance point between the incumbent protection and the secondary user’s QoS

  • The importance of spectral resources

  • Need more improvements for the 802.22 draft

Cognitive Radio Network: Enabling New Wireless Broadband Opportunities


ad