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 2018/11/14 Cognitive Radio Network: Enabling New Wireless Broadband Opportunities

Cognitive Radio Network: Enabling New Wireless Broadband Opportunities Outline Introduction Regulatory Scenario Overview of The 802.22 Standard Spectrum Management Model Conclusions Comments 2018/11/14 Cognitive Radio Network: Enabling New Wireless Broadband Opportunities

Cognitive Radio Network: Enabling New Wireless Broadband Opportunities 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. WiFi, WiMax, Cellular system 3G … different advantages and drawbacks In rural communities and emerging markets Technical aspects : Coverage and capacity [2] Experiences in using WiFi for Rural Internet in India 2018/11/14 Cognitive Radio Network: Enabling New Wireless Broadband Opportunities

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 aware of its environment and uses the methodology of understanding- by-building to learn from the environment and adapt to statistical variations in the input stimuli Tech Objective 2018/11/14 Cognitive Radio Network: Enabling New Wireless Broadband Opportunities

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 2018/11/14 Cognitive Radio Network: Enabling New Wireless Broadband Opportunities

Cognitive Radio Network: Enabling New Wireless Broadband Opportunities 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 2018/11/14 Cognitive Radio Network: Enabling New Wireless Broadband Opportunities

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 Ultra Wide Band tech for short-range 2018/11/14 Cognitive Radio Network: Enabling New Wireless Broadband Opportunities

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. 2018/11/14 Cognitive Radio Network: Enabling New Wireless Broadband Opportunities

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) CDT 2018/11/14 Cognitive Radio Network: Enabling New Wireless Broadband Opportunities

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 2018/11/14 Cognitive Radio Network: Enabling New Wireless Broadband Opportunities

Regulatory Scenario (cont’d) Protection of Incumbents PFA is important for the secondary systems’ QoS and efficient spectrum utilization [13] 2018/11/14 Cognitive Radio Network: Enabling New Wireless Broadband Opportunities

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 2018/11/14 Cognitive Radio Network: Enabling New Wireless Broadband Opportunities

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) 2018/11/14 Cognitive Radio Network: Enabling New Wireless Broadband Opportunities

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 Borrow some of the basic concepts from the IEEE 802.16 standard[14] 2018/11/14 Cognitive Radio Network: Enabling New Wireless Broadband Opportunities

Cognitive Radio Network: Enabling New Wireless Broadband Opportunities 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) 2018/11/14 Cognitive Radio Network: Enabling New Wireless Broadband Opportunities

Cognitive Radio Network: Enabling New Wireless Broadband Opportunities 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 2018/11/14 Cognitive Radio Network: Enabling New Wireless Broadband Opportunities

Cognitive Radio Network: Enabling New Wireless Broadband Opportunities 2018/11/14 Cognitive Radio Network: Enabling New Wireless Broadband Opportunities

Cognitive Radio Network: Enabling New Wireless Broadband Opportunities 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 Two important capabilities Overlapping of data transmissions and sensing on the same channel (or even adjacent channels) may negatively impact the sensing performance, resulting in a high rate of false alarms, especially given the very low IDTs to be met by the CPE’s spectrums sensing module (see TABLE I. ). The number of QPs scheduled should also be limited to a minimum necessary to achieve the required sensing reliability in terms of PD and PFA parameters 2018/11/14 Cognitive Radio Network: Enabling New Wireless Broadband Opportunities

Cognitive Radio Network: Enabling New Wireless Broadband Opportunities 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 2018/11/14 Cognitive Radio Network: Enabling New Wireless Broadband Opportunities

Cognitive Radio Network: Enabling New Wireless Broadband Opportunities 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) 2018/11/14 Cognitive Radio Network: Enabling New Wireless Broadband Opportunities

Cognitive Radio Network: Enabling New Wireless Broadband Opportunities 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 2018/11/14 Cognitive Radio Network: Enabling New Wireless Broadband Opportunities

Cognitive Radio Network: Enabling New Wireless Broadband Opportunities 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) 2018/11/14 Cognitive Radio Network: Enabling New Wireless Broadband Opportunities

Cognitive Radio Network: Enabling New Wireless Broadband Opportunities 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 Base on location information 2018/11/14 Cognitive Radio Network: Enabling New Wireless Broadband Opportunities

Cognitive Radio Network: Enabling New Wireless Broadband Opportunities 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 2018/11/14 Cognitive Radio Network: Enabling New Wireless Broadband Opportunities

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 2018/11/14 Cognitive Radio Network: Enabling New Wireless Broadband Opportunities

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 2018/11/14 Cognitive Radio Network: Enabling New Wireless Broadband Opportunities

Spectrum Management Model (cont’d) 2018/11/14 Cognitive Radio Network: Enabling New Wireless Broadband Opportunities

Cognitive Radio Network: Enabling New Wireless Broadband Opportunities 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 2018/11/14 Cognitive Radio Network: Enabling New Wireless Broadband Opportunities

Cognitive Radio Network: Enabling New Wireless Broadband Opportunities 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 system level evaluation to assess the robustness of 802.22 with respect to both data transmission and sensing against interference from other 802.22 cells. 2018/11/14 Cognitive Radio Network: Enabling New Wireless Broadband Opportunities

Cognitive Radio Network: Enabling New Wireless Broadband Opportunities 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 2018/11/14 Cognitive Radio Network: Enabling New Wireless Broadband Opportunities