In the early 1990s, software radio became a hotspot in mobile communications, when many people viewed the technology as a complex RF (radio frequency) and IF (intermediate frequency) processing problem required by modern multimode/multiband mobile terminals. solution. Today, software radio is seen as a technology for reconfigurable terminals in all phases of design, production, and use.
This article describes the concepts of software radio and reconfigurable technology. The concept of providing a terminal reconfigurable protocol stack is like the concept of software download, and will be adopted in 3G and future 4G standards.
First, software radio overviewSoftware Radio Technology is a new radio technology developed in recent years with the rapid development of microelectronics and computer technology. Compared with traditional ASIC-based wireless technology, it is flexible, versatile and upgraded. Convenient and other features. The core of its technology is that with the continuous advancement of large-scale integrated circuit technology and the continuous improvement of chip processing speed, software is used to complete various digital signal processing previously implemented by ASIC on DSP chip or general-purpose CPU chip platform. Features.
However, due to the limited level of technology such as broadband antennas, high-speed A/D and DSP, the conditions for implementing an ideal software radio platform are not yet available. Therefore, the research on software radio now focuses on the research of the above-mentioned key technologies, and on the other hand, it is more to study how to maximize the versatility and flexibility required by software radio under the existing technical conditions. The software design and generalization design ideas are embodied in specific application practices.
Second, the key technology to achieve software radioThe software radio adopts an open modular design, which makes the radio service function and the hardware platform relatively independent, which can bring a series of benefits. However, due to the limitation of hardware level and the theory of architecture, the ideal software radio can not be realized immediately. The "bottleneck" of software radio includes broadband antenna and RF module, broadband A/D conversion, high-speed DSP device, etc. .
1. Broadband antenna and RF module
Software radios can operate in multiple bands, and broadband, low-loss antennas must be used. Several octave antennas have been developed in the United States, but the efficiency is too low. The RF front-end also requires a wide frequency range, such as low-noise amplifiers, filters, power amplifiers, AGCs, etc. There is no technical difficulty. There are already related products on the market, such as Mini Circuits' MAR series broadband low noise amplifiers. Can meet the requirements.
2. Broadband A/D conversion
A notable feature of software radio is that the A/D conversion is as close as possible to the antenna, at least for A/D conversion of the intermediate frequency, which requires high performance of the A/D converter. The parameters for evaluating the performance of the A/D converter include signal-to-noise ratio (SNR), spurious free dynamic range (SFDR), intermodulation distortion (IMD), sampling rate, and sampling accuracy. The main two are sampling rate and sampling accuracy. Generally, these two indicators are comprehensively expressed by SNR. The SNR can be calculated by the following equation: SNR=6.02B+l.76+101og10(fs/2fmax)(dB), where B is the number of bits of the ADC, and fs is the sampling rate. Fmax is the highest frequency of the input analog signal. For a 70MHz IF signal, if the sampling accuracy is required to reach 12 bits and the SNR is equal to 80dB, the sampling rate can be calculated to be 558MSPS.
3. High speed DSP
Software radio is to digitize the entire working frequency band (about 25MHz). The intermediate frequency and baseband processing all adopt digital signal processing to realize software control. It puts high requirements on the processing power of DSP chip. Taking cellular mobile communication as an example, the system frequency band is 12.5 MHz, and the sampling frequency when oversampling is 30.72 MHz. After sampling, frequency conversion, filtering, extraction, etc., each sample is processed at least 100 times, and the processing rate is 3072 MOPS. . There are two solutions: one is to use multiple DSP chips for parallel processing. The Speakeasy I system uses this method. It uses TI's Quad C40MCM chip module, which consists of 4 TMS32 C40 and 5Mbyte RAM. l100MIPS (16bit) and 200MFL0PS (32bit) processing speed, I / O rate is 300Mbit / s. The second is to use a special programmable chip to down-convert the intermediate frequency and then perform DSP processing. Harris' digital downconverter (DDC) HSP500l6 performs the function of extracting useful signals from wideband signals with a maximum input rate of 75 MSPS (16 bits), which can be programmed to control data rates and data output formats. At present, the software radio system using DDC is quite realistic. Once the DSP device reaches the required level, it is easy to overexpose to the ideal software radio system.
Third, software reconfigurationSoftware reconfiguration provides roaming, low terminal cost, dynamic frequency dive management, fixed errors, new features, third party joins, additional value and personalization of network operations. The open software architecture allows terminals to become programmable transmitters for use in radio, television, home networks and offices, ie fixed mobile broadcast integration. Reconfiguration through upgrade software can accommodate rapid cycle times for future innovation and elimination.
The main benefits of the terminal and integrated circuit platforms that can be reconfigured by downloading new software are listed below:
1. Reduce the number of different modes. Reconfigurable technologies should allow for the manufacture of fewer types of terminals to support different technical standards. This has led to the development of large-scale terminal manufacturing in the direction of low unit cost.
2. The last minute or delay specialization. Using download means that the final configuration of the terminal should be after deployment, which increases the functionality of the product and reduces the likelihood of any product recall or return.
3. Runtime application. End-user applications such as games will be the first to be used in future applications running on future terminals.
4. Open platform. If an open platform is introduced, third-party developers will be able to develop innovative applications for the terminal that will increase the appeal of the terminal to end users.
Disadvantages of downloading software include the difficulty of managing different versions of software deployed on different terminals in the field and how to ensure their robustness in all user environments.
Reconfigurable features require software radios to change the criteria designers need to consider. As pure processing power dominates the current 2G wireless environment, programmable features are becoming the focus of software radio design applications.
DSPs and FPGAs can be easily reconfigured to implement various functions of software radio design. Existing communication ASICs offer better performance at a lower cost, but provide very limited programmability.
Determining the processing functionality of the device can be illustrated by a base transceiver architecture that supports both W-CDMA and GSM. Since W-CDMA employs spread spectrum communication technology, many users can share a single radio frequency (RF) channel. Between the uplinks 1,920 to 1,980 MHz and the downlink 2,110 to 2,170 MHz, the W-CDMA signal occupies a bandwidth of 5 MHz in each channel.
On the other hand, in each RF channel of the GSM system, the narrowband TDMA technology generally only supports 8 users. Between 890 and 915 MHz on the uplink and 935 to 960 MHz on the downlink, each channel of the narrowband TDMA occupies a 20 OkHz bandwidth.
In order to effectively balance the differences between the above standards in the software radio architecture, the digital upstream and downstream converters of the intermediate frequency (IF) processor must provide programmable channel selection, filter configuration, and sample ratio adjustment. The use of any ASIC signal processing device will bring unforeseen risks to future upgrades, so IF processing must also use FPGA or DSP devices. As more and more signal processing comes from digital IF inputs, processing algorithms become more specialized, limiting the ability of a single ASIC device to meet the required programmable requirements, while FPGA or DSP implementations are a bit more Good choice.
Fourth, download a new air interfaceThe final software reconfiguration of the terminal is seen by many as downloading a new air interface. Increasing power and reducing the cost of digital signal processing will allow for the use of reconfigurable baseband processing on mobile handsets, which will gradually allow the use of flexible air interfaces.
This will give consumers a terminal that can work with any network without significantly increasing terminal costs. This vision also benefits terminal/IC manufacturers because it allows RF manufacturing and baseband processors to adapt to all visible standards and markets. One of the main benefits of such a terminal to the end user is the ability to roam between many different air interface standards. Manufacturing a terminal for air interface reconfiguration requires three key elements
1. Software radio. Use as much software radio as possible to implement radio processing. Hardware reconfiguration is possible, but usually costs more than software implementation.
2. Standard. Terminal reconfiguration running on the new air interface standard will require a standardized protocol for transporting, authenticating and downloading software.
3. Software architecture. The software architecture in the terminal can be completely changed in the non-working state, or constructed in such a way that the key parts of the protocol software can be easily changed without affecting the terminal cost.
Terminals that use SDR to provide third-generation capabilities will be commercially available in approximately three years. A key benefit of the column terminal manufacturer is that SDR technology will allow the use of a hardware and software architecture platform to adapt to the world market. The SDR Forum estimates the size of the SDR terminal market and believes that by 2005 it will be approximately 130 million handheld devices.
V. Future standardsMobile communication technologies continue to advance, providing mobile users with greater bandwidth and many different services. One possible evolutionary path for GSM mobile networks is the evolution from GSM, which is dominated by voice services, to the 3G (UMTS) standard, which has the ability to provide users with high bandwidth for many business possibilities. The evolution of GSH is triggered by the use of the GSM standard extension; both HSCSD (High Speed ​​Circuit Switching) and GPRS (General Packet Radio Service) provide high data rates. The latter also provides packet data capabilities.
One possible evolutionary path for software downloads is to use a simple menu download of the SIM Application Toolkit (STK), then WAP (Wireless Application Protocol) allows for more complex downloads, and then WAP (Wireless Application Protocol) allows for more complex downloads, This is followed by two MEXE (Mobile Station Application Execution Environment) standards for downloading applications. MEXE is based on WAP, and MEXE-2 is based on personal JAVA. Finally, full dynamic reconfiguration is achieved through download. The new standard to do this is being developed by 3GPP TSGT2/SWG/(MEXE). Because of the ability to increase reconfigurability, we need new standard forms. In the future, we will move from fixed standards to flexible standards. The challenge is to choose how to maintain a multi-vendor operating system. This is possible if the download takes place in a well-defined software architecture;
At present, the role of 3G or UMTS terminals is to facilitate the operation of mobile terminals having the functionality of providing many different Quality of Service (QoS) application data streams. Reconfiguration using lower layer protocols will increase the ability of the terminal to match the Qos required by the application.
The use of reconfiguration technology and software downloads will facilitate the development of 4G terminals, which will provide many different air interface optimization configurations for specific applications.
Because of the reconfiguration capabilities of the software, 4G terminals are expected to achieve multi-mode, multi-service and multi-standard. Complete software reconfiguration will also allow the development of new base stations and network infrastructure that will dynamically adapt to different traffic conditions, maximizing the efficiency of the limited resources (spectrum and bandwidth) available to the operator.
ConclusionIn the future, through the use of low-level reconfiguration techniques implemented by software radio, the terminal will have the ability to download new air interfaces and run new communication standards within the limits of the terminal hardware.
A manual pulse generator (MPG) is a device normally associated with computer numerically controlled machinery or other devices involved in positioning. It usually consists of a rotating knob that generates electrical pulses that are sent to an equipment controller. The controller will then move the piece of equipment a predetermined distance for each pulse.
The CNC handheld controller MPG Pendant with x1, x10, x100 selectable. It is equipped with our popular machined MPG unit, 4,5,6 axis and scale selector, emergency stop and reset button.
Manual Pulse Generator,Handwheel MPG CNC,Electric Pulse Generator,Signal Pulse Generator
Jilin Lander Intelligent Technology Co., Ltd , https://www.jilinlandermotor.com