cognitive radio network enabling new wireless broadband opportunities
Download
Skip this Video
Download Presentation
Cognitive Radio Network: Enabling New Wireless Broadband Opportunities

Loading in 2 Seconds...

play fullscreen
1 / 30

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


  • 433 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

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
Outline
  • Introduction
  • Regulatory Scenario
  • Overview of The 802.22 Standard
  • Spectrum Management Model
  • Conclusions
  • Comments

Cognitive Radio Network: Enabling New Wireless Broadband Opportunities

introduction
Introduction
  • 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
Introduction (cont’d)
  • 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
Introduction (cont’d)
  • 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
Regulatory Scenario
  • 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
Regulatory Scenario (cont’d)Dynamic 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
Regulatory Scenario (cont’d)Dynamic 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
Regulatory Scenario (cont’d)Protection 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
Regulatory Scenario (cont’d)Protection 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
Regulatory Scenario (cont’d)Protection 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
Overview of the 802.22 standard
  • 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
Overview of the 802.22 standard (cont’d)The 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
Overview of the 802.22 standard (cont’d)The 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
Overview of the 802.22 standard - The 802.22 MAC(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
Overview of the 802.22 standard - The 802.22 MAC(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
Overview of the 802.22 standard - The 802.22 MAC(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
Overview of the 802.22 standard - The 802.22 MAC(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
Overview of the 802.22 standard - The 802.22 MAC(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
Overview of the 802.22 standard - The 802.22 MAC(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
Overview of the 802.22 standard - The 802.22 MAC(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
Overview of the 802.22 standard - The 802.22 MAC(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
Overview of the 802.22 standard - The 802.22 MAC(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
Spectrum Management Model
  • 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
Spectrum Management Model (cont’d)
  • 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
Spectrum Management Model (cont’d)

Cognitive Radio Network: Enabling New Wireless Broadband Opportunities

overview of the 802 22 standard the 802 22 mac cont d superframe and frame structures28
Overview of the 802.22 standard - The 802.22 MAC(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
Conclusions
  • 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
Comments
  • 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