multi standard multi-band receivers for wireless applications

Editor's Notes

• #2: Research Assist (National Telecommunications Institute (NTI))Post Graduate Student (Ain-Shams University)
• #4: Bluetooth and WLAN Coexistence Challenges and Solutions
• #5: Current and future mobile terminals become increasingly complex because they have to deal with a variety of frequency bands and communication standards.The current trends call for designs that allow: *Smooth migration to future generations of wireless standards with higher data rates for multimedia applications;Convergence of wireless services allowing access to different standards from the same wireless device;Current and future mobile terminals become increasingly complex because they have to deal with a variety of frequency bands and communication standards. Achieving multi-band/multi-mode functionality is especially challenging for the radio frequency (RF)-transceiver section, due to limitations in terms of frequency-agile RF components that meet the demanding cellular performance criteria at costs that are attractive for mass-market applications.This requires designs that work across multiple wireless standards, can easily be reused, achieve maximum hardware share at minimum power consumptionlevels particularly for mobile battery-operated devices.While serious efforts are currently underway to develop highly integrated solutions for digital basebands covering multiple standards, today’s emerging multi-standard, multi-band wireless devices use "stacked" transceivers, i.e. separate transceivers for different standards. This represents a major bottleneck in attempting to achieve higher levels of integration and reduce the bill of material for a multi-standard wireless device. Development of radio architectures and mixed-signal design solutions that support multiple standards is therefore needed.
• #7: Behavioral Modeling, Simulation and Synthesis of Multi-standard Wireless Receivers in MATLAB/SIMULINK
• #12: Cost efficiency: Cost efficiency for each technology deployment (with reference to a single user)Coverage: Coverage of each technology (area covered by a single access point)User penetration: Current number of users/terminalsThroughput: Each technology and standard throughputCost/bit: Each standard cost per bitRange: Max. distance to access pointMobility: Each technology mobility useFrequency: kind of frequency, licensed or not licensed, regulated at local or global level, etc
• #14: In this work we closely consider the multi-standard system, which may support different air-interfaces.
• #17: A multiband receiver is a radio capable of receiving a wide range of radio frequencies.Obviously, each of them has different center frequency, channel bandwidth, noise levels, interference requirements, transmit spectral mask, and so on.As a consequence, the performances of all building blocks in the transceiver must be reconfigurable over an extremely wide range.
• #19: multi-standards, multi-bands, multi-modes, and multi-protocols systems
• #20: Multi-mode Transceiver: a radio-frequency (RF) transceiver to deliver and to be reconfigured into every imaginable operating mode, in order to comply with the requirements of all existing and even upcoming communication standards.Moreover, a user can be connected to the cellular network by means of GSM or UMTS and synchronize his/her e-mail, update his/her photo gallery by the closest wireless Internet connection, for example, Wi-Fi based on IEEE 802.11gThe lack of all these system is an analog baseband level, which does not allow to the system to reuse the resources for the best performance. This leadsresearchers to look ahead for the digitalization of the terminal architecture and to move digital signal processing as closed as possible to a radio frequency (RF) front-end. In this situation software defined radio (SDR) technology can be one of the possible solutions.
• #23: The interface and interconnections must be friendly and easy to understand for a user.Moreover, the MT must adopt a new network configuration smoothly and without a particular hardware installation. To do that, all what it needs is to update or to upgrade the current system software and continue to work with new settings. This feature of the MT can be supported only in case if the MT has a flexible and reprogrammable architecture that allows the system manipulation through the network access.Nevertheless, manufactures are who accumulates all new technologies inside a unique device. Thus, manufactures must follow both directions first to satisfyuser wishes and second to reply to provider requirements. The novel approaches in the hardware base of the MT push manufactures consider the combinations of these technologies on the single platform.To satisfy to many of these requirements the MT must have a reconfigurable system that allows to install necessary applications, to update current configurations, to switch between networks dynamically, and to take advantages of released standards via downloading them. One of the recent approaches to solve the paradigm of reconfigurability is the SDR technology. The SDR technology allows to MT to dive in the heterogeneous architecture of current wireless environment, to manipulate with different parameters in order to accomplish the best combination to provide the high level QoS.
• #24: Since the initial commercial introduction of the advanced mobile phone system (AMPS) service in 1983, mobile communication has seen an explosive growth worldwide.Besides the frequency reuse capabilities provided by the cellular operation, advances in technologies for wireless access, digital signal processing, integrated circuits, and increased battery life have continued the exponential growth in mobile and personal communication services.Systems are cellular or wide area networks (WAN), cordless telephony, satellite mobile, paging and other specialized mobile radio systems including wireless system for local, personal and metropolitan area networks (LAN, PAN and MAN). Whereas the analog cellular mobile systems fall in the category of first generation mobile systems, the digital cellular, low power wireless, and personal communication systems are perceived as second-generation mobile systems. The emerging Internet environment urgently requires support for asymmetric, interactive, multimedia traffic based on high-speed packet data transport. Such rapidly growing service requirements, driven by the global users of telecommunications, will dramatically change the nature of telecommunication services in the twenty-first century. The underlying vision for the emerging mobile and personal communication services for the new century is to enable communication with a person, at any time, at any place, and in any form, with a paradigm shift from the current focus of voice and low speed data services to high speed data and multimedia services.The current second-generation digital mobile and personal communication systems are based on national or regional standards that are optimized for region or country-specific regulatory and operating environments. They are therefore unable to interoperate with each other and can provide mobility only with their radio environments as well as within geographic regions in which a specific standard is operational.Efforts are therefore under way at the international as well as the regional/national levels to develop the so-called third-generation mobile telecommunication system that will meet the coming needs of telecommunications subscribers.
• #25: TACT is a multi-standard RF transceiver architecture comparison tool.Use TACT to design the multi-band multi-standard transceiver at high level.The use of TACT eases the design of physical circuits able to be dynamically re-configured.
• #28: Circuits and Systems for Future Generations of Wireless Communications
• #30: Even in the single standard case, the level of complexity of a wireless communications receiver is enormous. When the multi-standard case comes into the picture, this problem is aggravated. The design of a multi-standard system is substantially more complex than the combination of the system level design of separate single-standard systems. One of the main challenges multi-standard systems have to overcome is interference. The increasing complexity of multi-mode systems entails the presence of many on-chip signals that may act as potential interferers to the neighboring systems. Therefore the need of designing a careful frequency planning that takes into account the signals coming from all the standards. Careful layout and on-chip isolation mechanisms should not be forgotten later in the design cycle. The advantage of programmable blocks and architectures comes in terms of re-usability, flexibility, and area and power consumption. Moreover, using digitally tunable blocks allows to compensate for process variations and other effects that greatly affect analog circuits increasing, thus, the reliability of the overall system . However, adding programmability entails an extra design effort that may not pay off in terms of performance. As opposed to a fully stacked solution, hardware reuse favors in principle the area reduction sought in multi-standard systems. But... shall we use programmable blocks that can handle several operation modes in all cases or is there any block that should be duplicated? Is a stacked solution that bad? In some cases, it may actually pay off having a completely independent signal path for some of the target standards. How do we decide that? 1) One bit re-configurationThe simplest re-configuration would be to switch between standards on a very high level. This would require an independent baseband implementation for each system. At some place the incoming data stream is multiplexed to the dedicated baseband processing chain and the processed data is given back to the data sink. The amount of needed information for re-configuration is at minimum one single bit, defining the multiplexer behaviour. Though this approach may be good enough for some dedicated basestation applications, it is not applicable for terminal applications as power consumption and area efficiency are the dominating factors for high volume, mobile devices. 2) Software Defined RadioThe most flexible re-configurable architecture is a Software Defined Radio (SDR) one [2], where the same device can be re-programmed to support various standards. Software defined radio architectures are building a general purpose communication platform for existing wireless access technologies, including future extensions and enhancements. Therefore the hardware platform has to provide sufficient processing power and communication bandwidth for future needs. The openness of this approach concerning enhancements and new features results in an overhead of available resources, which is infeasible from a terminal point of view. In addition, high-bandwidth communication systems such as 54 MBit/s Wireless LAN would require a massively parallel implementation of microprocessor and DSP resources in order to fulfill the performance requirements. They would contribute mainly to the power consumption and area overhead of the system. 3) Re-configuration by parameterizationTherefore we propose a new terminal approach, in which similarities and differences between the standards will be identified and parameterized. The basic algorithms, underlying the systems, have been evaluated and classes of algorithms with their corresponding parameter sets have been identified. Dedicated hardware will be developed now for the common baseband structures. Differences are accommodated by reconfiguration based on the defined parameters. Re-configuration capabilities will be provided only as much as needed, but as few as possible. This approach will be named Software Re-configurable Radio(SRR). The system architecture, which is underlying this SRR, has to be scalable and modular in order to allow future extension of the system, without changing the main part of the system architecture itself. Therefore, SRR can be implemented efficiently and power optimized.
• #34: Each manufactory searches for the possible integration of a new technology into the platform with already implemented old technologies. In this case the terminal became fully compatible. However, an addition of a new unit can increase the size and the weight that can provoke less market activities.
• #35: From a user point of view, new technologies create new devices and a user does not want to carry all of them. User needs a unique single terminal that meets the needs requirements.So the functionality must be realized in a software implementation and a digital environment.
• #36: Zero level: the device functionality can be reconfigured by changes of a hardware level.First level: supports Software-Controlled Radio. In such kind of devices, there is no a possibility to change a modulation type or a frequency band. However,these devices can support various standards by applying some program controlled transceivers. For example, mobile phones with GSM/CDMA technology existence or Wi-Fi access points with two frequency range based on different versions of the IEEE 802.11 standard.Second level: presents SDR modules, where a user can handle a frequency band, a modulation type and a hopping type.Third level: is an Ideal Software Radio. All components are digital, only in a mobile phone case there is an exception which consists of an analog antenna,a microphone and a dynamic, that must be analog. The SDR Forum is oriented on these type devices which will allow to make an essential progress in the telecommunication area.Forth level: is a Ultimate Software Radio. The SDR Forum determines that in these kind devices to control and manage traffic will be possible, also to support a wide frequency range, different air interfaces and applications. At the same time, a device can instantly switch between interfaces and track a location of a user by using GPS, broadcast video on a mobile device from a closest station, and use satellite channels.
• #37: The concept of SDR is a complex paradigm that involves fundamental technologies implemented in various types of hardware and software platforms.These technologies include the generic hardware implementations of GPP, RF components, DSP chips, A/D converters, and smart antennas to provide multiple functionalities:Reconfigurability:The system must provide the requisite services for which it was designed and installed. So, the keynote of any MT is its ability to support the needs of a user. The system must provide the necessary services across the spectrum of requirements. In this sense the problem of adoptability is appeared.This obstacle is inherent for hardware units where the presence of new software can involve the resource reconfiguration and relocation. However, by means of the SDR technology MT digital baseband level must easy accept a new configuration and provide correct its execution. The recent hardware technologies allow reorganizing the software sources’ location and thus the system reconfigurability is supported [12]. We must note that the ability of SDR-based systems to reconfigure to alternative radio architecture builds a bridge not only for the transmission modules at the physical level, but also for the information handling functionalities at higher levels including the application level and the human interface mechanisms.The reconfigurability via software exchange can play a role of a primary strength in the SDR determination. Interoperability:The ability of communications systems to operate with other communications systems, particularly when the systems belong to various transmission families. This property is mirrored in the ability of disparate systems to cooperate with each other in a seamless trend. This capability can be considered as a particular strength of SDR-based systems in that dynamic reconfigurability of operating parameters. The interoperability forms a fundamental basis for multi-standard systems that involve the interaction between various network infrastructures. Besides, on the baseband level of MT this ability becomes significant when there is a need to reconfigure the system according to the new protocol algorithm, and the data knowledge of the previous architecture are required. Moreover, in the scope of this ability, the form of these data must be compatible with the reading mechanism of a new protocol in order to let it know about the previous resource usage.Flexibility:The ability of the system to respond to a change and/or to a recover from a failure is crucial in establishing the resilience of the system. It refers to the system’s ability to evolve with software updates and changes to operational requirements. Because all of the functionality of the SDR-based system depends on inherent software, it is easy to change, modify, and test the functionality of a new digital baseband level configuration on new software as opposed to the development of a new hardware unit [49]. Furthermore, it is also easy for SDR-based system to recover from faults and to change to new demands on the system through simple software modifications. Modularity:The modular structure of the SDR-based systems allows the generic architecture to be independent of existed RATs, processing protocol algorithms, and technological platforms. This feature is involved into the deep analysis of baseband level structures based on SDR implementations.The core concept of modularity is oriented at the selection of appropriate hardware or software unit to perform the required function. Besides the fixed configuration of these hardware units must be avoided in sense to increase the resource usability. Thus the same hardware can be adopted for the different system needs. However, software modularity involves source relocation. In other words, the same software function can be used in different system algorithms by means of a property inheritance that decreases the system memory storage and loading.Upgradeability:This feature addresses to the system’s ability to adapt and grow with expanded requirements and users. The system flexibility can be measured by means of adjusting changes in the system operational scope. Since SDR-based systems rely on software to define characteristics, hence the system can smoothly move on into the functionality of the system based on changes of the operating software. Thus, for example version 1.1 of an operating system can recover all bugs in version 1.0 as well as expand on the previous functionality.  
• #39: As this picture shows, the Digital Signal Processing is the central component in the realization of the SDR structure. The special attention should be drawnto the choice of DSP processor and its main features. All possible functions are executed in the transceiver baseband level presented by the digital architecture. Due to this solution, we are able to implement all processing in the digital environment.
• #40: Programmable hardware is increasing and being used in digital radio systems at different functional levels. The SDR technology aims to take advantagesof the programmable hardware to build an open software architecture based on the radio system.Today the description of the baseband level for wireless communication systems is done by means of a digital implementation. This means that most of functions of the signal processing chain have a software nature and can be run by low level coding for the particular hardware platform, for example DSP or FPGA.The SDR technology makes possible to place numbers of modules on a single platform. That feature has shown that a description of full baseband signalprocessing for different protocols can be adopted by this hardware platform and not only one RAT can be integrated.