COGEU. D3.1 Use-cases Analysis and TVWS Systems Requirements

Transcription

1 COGEU FP7 ICT COgnitive radio systems for efficient sharing of TV white spaces in EUropean context D3.1 Use-cases Contractual Date of Delivery to the CEC: July 2010 Actual Date of Delivery to the CEC: 2 nd August 2010 Author(s): Hervé Aïache (TC), Damien Lavaux (TC), Stéphane Rousseau (TC), Paulo Marques (IT), Joseph Mwangoka (IT), Jonathan Rodriguez (IT), George Kormentzas (AEGEAN), George Mastorakis (AEGEAN), Evanggelos Pallis (AEGEAN), Athina Bourdena (AEGEAN), Stavros Stavrou (SIGINT), Evagoras Charalambous (SIGINT), Álvaro Gomes (PTI), Helder Alves (PTI), Juergen Dieterle (IRT), Georg Schuberth (IRT), Andreas Sieber (IRT), Aneta Baier(IRT), Raul Schramm(IRT), Juergen Lauterjung (R&S), Christoph Balz (R&S) Work Package: WP3 Est. Person Months: 25 Security: PU Nature: Report Version: 1.0 Total number of pages: 137 Abstract: This deliverable reports the work performed in COGEU tasks T3.1: Use-Cases Analysis & System Requirements and T3.2: Broadcast Networks and Mobile Networks Mutual Interaction. The main objective of D3.1 is to extract the COGEU system level requirements by jointly analysing the COGEU use-cases requirements (T3.1) and examining the constraints imposed for robust incumbent protection (T3.2). A reference model designed to accommodate the COGEU system requirements is also an important output of this deliverable and will be the basis for future COGEU system architecture developed in WP3. Keyword list:, Use Case Analysis, System Requirements, Compatibility Criteria Page 1 of 137

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3 Executive Summary This deliverable reports the work performed in tasks T3.1: Use-Cases Analysis & System Requirements and T3.2: Broadcast Networks and Mobile Networks Mutual Interaction. The main objective of D3.1 is to extract the COGEU system level requirements from the use-cases identified in D2.1. This is achieved by jointly analysing the COGEU use-cases requirements (T3.1) and examining the constraints imposed for robust incumbent protection (T3.2). A reference model designed to accommodate the COGEU system requirements is also an important output of this deliverable and will be the basis for future COGEU system architecture developed in WP3. In D2.1, six use-cases were selected as important for the COGEU project because of their market potential. These are as shown in Table 1. System UMTS extension over LTE extension over WiFi with cognitive access to DVB-H with cognitive access to Public safety applications with cognitive access to PMSE with cognitive access to Spectrum Regime Secondary spectrum market Secondary spectrum market Spectrum commons with cognitive functionality Both commons and secondary spectrum market Secondary spectrum market with prioritization mechanisms. Spectrum commons with cognitive functionality Page 3 of 137 Table 1: COGEU systems with respective spectrum sharing modes over TV white spaces Key conclusions: On COGEU Use Case Analysis: The LTE network can be deployed on many carrier bandwidths (1.4, 3, 5 10, 15 and 20MHz) which provides flexibility on the deployment of LTE on the. Putting capacity and coverage together, it is possible to expect that if the LTE is operating in the band it will be possible to enhance the overall system quality of service (QoS) and provide rich content data to more users at lower price. If a PMSE (typically a wireless microphone link with 200 KHz bandwidth), is transmitting on a UMTS cell operating in, all the UMTS transmissions on the band are stopped, because UMTS signals are spread over the 5MHz bandwidth through DS-CDMA. But on LTE, different sub-carrier can be allocated dynamically based on the radio channel quality and sub-carriers availability. What means that if a primary user is using a band to transmit only the sub-carriers of the LTE carrier on that band will be blocked the remaining could continue to be used. Despite the LTE dynamic behaviour and adaptability, some services and particularly real time services that do not have packet retransmissions capabilities, due to service delay constraints, should avoid the because PMSEs transmission can start between sensing times creating errors that cannot be corrected. channels are well suited for unlicensed broadband wireless Internet services (also designated Wi-Fi over. Access to vacant TV channels would facilitate a market for low-cost, high-capacity, mobile wireless broadband networks. The favourable range and penetration characteristics of signals compared to ISM band signals could also result in installations with significantly less infrastructure and thus less cost of deployment. Wi-Fi over, within the scope of COGEU, will operate mainly under the spectrum of commons regime. This will reserve the characteristics of Wi-Fi as an affordable access

4 Page 4 of 137 technology but it will be enhanced by the better propagation characteristics of the UHF bands when compared to higher frequency bands. Using a combination of sensing and a broker with database access to known frequency allocations and other relevant information, a controller entity will be able to make sure that the access points operate at the right frequency. Cognitive radio mechanisms integrated within an interactive Mobile TV network to operate in will enable for the provision of additional multimedia mobile services in Europe. The proposed mobile TV over use case is based on a DVB-H system, which is able to operate as a secondary cognitive radio network. The DVB-H operating in is able to sense TV spectrum in order to avoid possible interference caused to other licensed systems not registered in the database and negotiate via a broker temporarily spectrum rights. In cases where wireless mesh network deployed for Public Safety agencies experience deficiency or just unavailable (e.g. it has not been deployed yet or because it has been affected by the threats); within the framework of COGEU, novel approaches can provide the best network capacity to access all required information and communications to ensure the most efficient intervention exploiting. Cognitive radio networks and Software Defined Radios can dramatically improve the efficiency of public safety interventions and their role in prevention. The centralized point in the COGEU system allows, in the event of an emergency, a higher priority policy to be propagated into the spectrum broker temporarily rescinding nonemergency utilization of the in the specific areas of need. Moreover, service prioritization can be incorporated into the database. Public Safety systems would have the highest priority. From technical point of view, one major challenge will be to support the Quality of Service needed by Public Safety applications while the is highly fragmented and partially available in time and space. PMSE is an established technology which has been used over many years in areas of PWMS (professional wireless microphone systems); talk back systems and Wireless audio links. For better co-existence with new user entrants, within the scope of the COGEU project, cognitive PMSE (C-PMSE) are proposed. The expected benefits of C- PMSE are improvements in terms of reliability, spectrum efficiency, productivity, and better coexistence with secondary TV white space users. On COGEU Mobility Requirements: System requirements for mobility management in COGEU use cases in TV white spaces were identified. Traditional mobility management mechanisms, when applied to cognitive radio wireless networks in, may cause significant performance degradation because of ignoring spectrum uncertainty issue prevalent in secondary spectrum usage. Challenges arising from cognitive radio wireless networks in call for the design of new mobility management techniques considering the environmental features that influence connectivity in temporal, spatial and frequency domains. The problem of mobility management in the context of secondary spectrum usage has been investigated in various works, however, most of this works did not consider the current advancement in regulatory policy regarding geo-location databases, which reduces the devices complexity on spectrum sensing and increases the reliability and predictability of spectrum resource availability. For this matter, more spectrum efficient mechanisms can be developed to exploit the regulatory change and advance the realization of COGEU use cases. The information offered by the COGEU broker will be exploited in mobility management in a context awareness perspective. The system requirements for the mobility problem in TV white spaces include but not limited to operative interworking architecture, optimal choice of access technology, medium independent hand over (MIH), power saving, security, QoS, context awareness, etc. The target for the COGEU approach for mobility management in TV white spaces is to achieve the handoff latency of less than 50 ms in order to support most of real time applications. This will be achieved through pro-active context awareness enabled mobility management.

5 On Protection Requirements: The measurements on protection requirements reported in this deliverable are part of COGEU contribution to the CEPT Project Team SE43. The results presented are the basis for compatibility studies and assessments of the required criteria that a Cognitive Radio using LTE technology has to meet in order to operate in the UHF broadcast band without causing harmful interference to DVB-T reception. If Cognitive Radio using LTE technology is designed to fit the 3GPP spectrum mask currently applicable to user equipment (UE), the required protection ratios against DVB-T for frequency offsets of more than 16 MHz are dominated by sideband emissions of the UE. They are relatively independent of the signal characteristics of the interfering LTE signal (e.g. in time domain). Co-channel protection ratios for DVB-T 16-QAM 2/3 are about +11 db, average adjacent channel protection ratios for 5 MHz wide LTE signals are about -20 db, and for high frequency offsets the value is about -30 db. Applying a more stringent spectrum mask to the LTE emission cannot generally improve the compatibility situation because even at average wanted signal levels, quite a number of DVB-T receivers already show overload effects that limit the maximum unwanted signal level. Lab measurements for the determination of the protection ratio for DVB-T against WiMAX, and vice versa were performed. In the former, the WiMAX signal represents the interferer to the DVB-T signal, which is normal since DVB-T is the primary user. In the later, the DVB-T signal represents the interferer to WiMAX secondary signal (COGEU system). For the determination of the protection ratio for DVB-T against WiMAX, two different interferer signals are modelled for the lab measurements: the signal of a WiMAX base station and the signal of a WiMAX mobile station. With each of the WiMAX signals, the protection ratio in the wanted channel is defined by the chosen DVB-T mode. For the chosen 16QAM mode this amounts to approximately +13 db. It is also clear from the measurements that the channel n+9 is more likely to show an increased sensitivity to interference signals due to the IF conversion. Although WiMAX is a secondary user, but still needs to consider the protection ratios which are required against the primary service, i.e. DVB-T. The purpose is to determine how the primary user would limit the performance of the secondary user (COGEU system). This information may be useful when the coverage for secondary services is planned. Initial lab measurements indicated that the protection ratio for co-channel interference is about +9 db. The chosen bandwidth of 10 MHz results in the WiMAX signal spilling over into the adjacent channels n-1 and n+1. If either of these channels carries a DVB-T signal, the protection ration is low, in this case about 0 db. Due to the limited selectivity of the WiMAX transceiver card, the protection ratios only improve (i.e. develop towards more negative values) about 2 or 3 channels away from the wanted signal (n = 0). The electromagnetic radiation of cognitive radio in a DVB environment potentially decreases the reception quality of the DVB service by increasing the existent noise floor. This decrease was classified and demonstrated by simulations, which showed the potential loss of DVB coverage. The loss depends directly on the protection ratio obtained by laboratory measurements. The simulation made in this investigation gives a tendency about maximum power levels of CR base stations dependent on the protection ratio. For the derivation of a maximum power level, an exclusion zone, wherein there is no potential interfered DVB-T receiver is defined. This could differ for certain scenarios (rural, urban, base station or handheld). In rural areas this exclusion zone could be set to a minimum of 170 m wherein there is no DVB-T receiver. If the CR uses an adjacent channel with PR = -30 db, simulation delivers a maximum power level of 10 dbm EIRP. In urban areas this exclusion zone could be set to a minimum of 20 m wherein there is no DVB-T receiver. If the CR uses an adjacent channel with PR= -40 db, simulations delivers a maximum power level of 0 dbm EIRP. However, up to now, there is no common accepted limit for the interference of CR. The criteria are still under discussion. Page 5 of 137

6 On Sensing and Geolocation Database Requirements: Sensing and geolocation requirements are compared in different regulatory domains (CEPT, OFCOM and FCC). Autonomous sensing techniques relay only on the power strength measured in the specific CR location. The decision whether a TV channel is occupied or idle is performed by comparing the measured power strength with a threshold level. CRs based on autonomous sensing can operate only low power \short range applications, usually using power far less than what it could use in reality. Analysis showed that it is not possible to set the maximum transmission power, simply based on the power strength detected by the CR device. Therefore COGEU adopts a hybrid approach where local sensing information is combined with geolocation database information to compute the spectrum pool. Interference analysis highlights that simple rules such as established by FCC, with fix power limits for CR operation (up to 4W for fixed devices, up to 100 mw for portable devices) regardless their geographic position doesn t take full advantage of potential. Rather than fix artificial limits for the transmission power, COGEU assumes that devices have power control mechanisms able to adjust the transmission power for an efficient exploitation of opportunities. Since COGEU applications consider realistic\affordable sensing devices and pursue efficient exploitation of, we will consider a hybrid approach where autonomous sensing and geolocation database are combined to compute the maximum transmission power in a specific location. Combining the two approaches can also relax the sensitivity required for sensing devices which a major limitation of developments. Also, since local sensing is only performed in a limited number of TV channels indicated by the database, the hybrid approach will speed up the sensing process. A preliminary COGEU frame structure fulfilling the sensing and database requirements is proposed in this deliverable. On the technology limitations: Important technical progress is still required with a view of mass market devices, such as, energy efficient Software Defined Radios, miniaturization, integration with other RATs and efficient compact antennas for mobile devices operating in TV bands. Because devices have to do spectrum sensing, database access and reconfiguration before transmitting, some delay sensitive services, such as voice service, should be considered when designing the RRM strategies (WP6). On the impact of regulatory developments in COGEU system: In order to protect incumbents, regulators such as FCC and OFCOM have limited the power level of CR devices assuming always the worst case scenario. This brings complexity in device design and limitations on transmitted power affecting the communications coverage and the type of services supported. Since COGEU applications consider realistic sensing devices and pursue efficient exploitation of, a hybrid approach where autonomous sensing and geolocation database are combined to compute the maximum transmission power in a specific location is considered. The COGEU hybrid approach has an added advantage of being future proof from a regulatory perspective. Currently, regulators such as the FCC are considering lowering or even eliminating the sensing requirements. This policy change will have a positive impact on the deployment of cognitive devices in that it will allow for cheaper systems and greener devices in terms of power conservation due to reduction in sensing overhead. With such regulatory changes on sensing requirements, COGEU systems will be able to more easily support real-time services. However, the need for harmonious co-existence with other TV white space users and incumbents will still remain. Therefore, at the system requirement level, the COGEU frame structure will simply be improved to re-configure the sensing requirements in relation to the negotiation mechanism to acquire spectrum context from the geo-location database or from Page 6 of 137

7 the COGEU broker. Other COGEU ongoing and future should also consider the regulatory changes in their solutions. On the COGEU Reference Model: COGEU will consider a centralized topology with a spectrum broker trading with players. The spectrum broker controls the amount of bandwidth and power assigned to each user in order to keep the desired QoS and interference below the interference limits. In the COGEU reference model, the centralised Broker (Figure 1) is an intermediary between the geolocation database (spectrum information supplier) and players that negotiate spectrum on behalf of spectrum users. Figure 1: COGEU reference model with cellular, WiFi and Public Safety networks operating in On the COGEU System Requirements: Robust incumbent protection and QoS provisioning impose significant design challenges and shape the design choices of COGEU system. The key COGEU system requirements are identified and listed in this deliverable as shown in Table 2. COGEU system requirement Incumbent protection Coexistence between secondary users Comment The system shall provide means to protect incumbent systems. COGEU approach is combining the use of geo-location database together with autonomous sensing. The database protects DVB-T and professional PMSE systems that can be planned in advance. The maximum allowed transmit power in a specific vacant DVB channel is computed based on cochannel and adjacent channel protection ratios. Other PMSE users such as ENG shall be protected trough autonomous sensing. The system shall be able to facilitate coexistence with other secondary systems operating in. This is done through dynamic allocation mechanisms based on protection rules specified for each combination (e.g. LTE over vs. WiMAX over ). Page 7 of 137

8 QoS requirements of secondary services Coverage The system should provide a means to support applications with different QoS parameters, such as transmission rate, delay and delay jitter. Thus, COGEU system should be flexible enough to satisfy different QoS requirements. Because devices have to do spectrum sensing, database access and reconfiguration before transmitting, some delay sensitive services, such as voice service, should be considered when designing the RRM strategies (WP6). The increase in range is proportional to the reduction in carrier frequency when compared to conventional systems (WiFi, LTE, etc). LTE cell at 700 MHz can have 10 Km radius and WiFi at 700 MHz can cover 340m. The path loss gain (e.g. a difference of 10 db comparing 700 MHz to 2.1 GHz) can be partly destroyed by inefficient compact antennas which is a constraint in the COGEU system design. Coverage is limited by the maximum allowed transmit power that depends on the co-channel and adjacent channels protection requirements implemented. The maximum allowed power is provided by the geolocation database. Mobility Secondary spectrum trading Mobility management shall be supported across heterogeneous cognitive radio networks in. The target for the COGEU approach for mobility management in TV white spaces is to achieve the handoff latency of less than 50 ms in order to support most of real time applications. This will be achieved through pro-active context aware enabled mobility management. The use of the spectrum in a secondary trading regime should track the most economically advantageous use of the spectrum in a more fluid and nimble manner than is possible under a Command and Control model. In line with the trading mechanism, price discovery is an important requirement to enable the Broker to allocate the spectrum to the most valuable players. Efficient spectrum policies to enable fairness in the spectrum sharing models needs to be implemented. COGEU considers a regulatory regime that allows a fast re-assignment of spectrum ownership. Efficient use of Service prioritization Maximum operation power and power control Location information Efficient use of will be achieved through dynamic allocation mechanism. Once the player needs spectrum resources it consults the Broker and provides its GPS location and intended emission power, spectrum mask, coexistence requirements, etc. After receiving the information, the Broker through its trading mechanism and price discovery matches the player requirement with available resource. Fragmentation of shall be minimized. The centralized point in the COGEU system allows, in the event of an emergency, a higher priority policy be propagated into the spectrum broker temporarily rescinding non-emergency utilization of the in the specific areas of need. Moreover, service prioritization can be incorporated into the database. Public Safety systems would have the highest priority. The maximum allowed power for operation is not pre-fixed. The power level is limited by the geo-location database information for protection of incumbent systems. Power control shall be implemented in COGEU transceivers. users should be able to provide its (geographic) location information to the Broker so that the database can provide spectrum availability information specific for that location. The system may obtain its location information through GPS, 100 m resolution is required. Page 8 of 137

9 Geo-location database access Initial access Autonomous sensing aggregation The system should be able to access geo-location database to retrieve spectrum availability information ( pool). The COGEU geolocation database and protocols will be specified in T4.2 (D4.1) The development of detailed procedure covering all the necessary aspects of the initial and periodic connections to the broker\database would be highly desirable. Autonomous sensing is mandatory for PMSE and optional for DVB-T signals (mainly protected by the geolocation database). Detection thresholds are adopted from current regulatory framework. The system should provide a signalling channel for reporting of local sensing data and supports centralised cooperative sensing. Spectrum aggregation techniques will be used to shape the CR signal (OFDM based) and to take advantage of fragmented opportunities. Frequency scanning Reconfigurable COGEU transceiver. Regulatory enforcement COGEU GUI Complexity System evolution Regulatory changes COGEU operation band starts from channel 40 to channel 60 (622 MHz- 790MHz). Efficient SDR platform, RF modules and compact antennas are required to operate in this band. The COGEU transceiver is based on a SDR platform; the detailed requirements are specified in T5.1 (D5.1). For regulatory enforcement, the database can be used in identifying the source of harmful interference where it occurs and may enable a remote de-activation of the device. The system should have a web interface able to allow players to follow the secondary market activity, communicate with the broker and negotiate spectrum rights in real time. The system should minimize complexity of the architecture and protocols. This will be achieved in part by using the geolocation database access that moves terminal complexity to the core network side. The price of the devices must be affordable to potentiate the market entrance, therefore COGEU will take into account the complexity and implementation challenges of the solutions investigated. The database shall have the ability to be dynamically updated to continuously adjust interference protection parameters in line with the evolution of incumbent standards (e.g. DVB-T2). In fact, COGEU must not block the evolution of incumbent systems. The COGEU system should be able take advantage of regulatory changes in incumbent protection requirements, like the reduction or elimination of autonomous sensing requirements considered by some regulators like the FCC. Table 2: COGEU systems requirements Page 9 of 137