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802.11p - Making Vehicles Talk



Vehicles have started mimicking human beings, they want to start talking to each other, as well as sharing information with each other. If vehicles start taking with each other, then they can have more  information on the surrounding environment and potentially act to increase safety of the passengers. If vehicles can talk to infrastructure, then it would be possible to make automatic toll  payment, take automatic action at traffic signal, make automatic diagnostics/maintenance and enable targeted commerce. Vehicle-to-vehicle (V2V) and vehicle-to-infrastructure (V2I) communications are gaining increasing importance in automotive industry. LabVIEW can support modeling and analyzing such  networks.

The wireless communication, also known as Dedicated Short Range Communications (DSRC), will be based on the IEEE 802.11p standard. The focus of DSRC  is to have connected cars to assist in driving and to increase safety.  The information shared through such communication may include vehicle, road and traffic conditions. The communication is not limited to vehicle-to-vehicle information; the protocol can be used to connect vehicles with infrastructure including utilities, traffic signals,  maintenance, owners and commerce. DSRC  communication is being targeted for safety applications (e.g., post  crash notification, cooperative collision warning etc), convenience  applications (e.g., congested road notification, parking availability  notification etc), and commercial applications (e.g., remote vehicle  personalization, diagnostics etc). The applications may also require  different types of communication – e.g., unicast vs. broadcast,  event-driven vs. periodic, download vs. streaming etc.

802.11p - The Background

802.11 p is based on the  IEEE 802.11 standard targeted towards in vehicle communications systems and applications of  wireless access in vehicular environments.
The signal is transmitted at 5.9 GHz and can move up to 54 megabits of data per second.  It uses Orthogonal Frequency-Division Multiplexing (OFDM), which is an efficient coding technique that splits the radio signal into several sub signals before they reach a receiver.  This greatly reduced interference between signals.

Table 1

* 802.11p is half-duplex; throughput at maximum bandwidth is 27 Mbps each direction
** Provides the 802.11a packet format in the 4.9 GHz band in Japan.

Table 1 - Characteristics of different IEEE 802.11 standards



The use of a flexible open platform makes the implementing any standard much easier. National Instruments, the leader in PXI, provides a system based on a single NI PXI chassis built on the latest PC technology for implementing and testing wireless RF protocols. The system is based on a high performance PXIe chassis integrated with an embedded high-performance controller, an open modular FPGA based instrument- the VST, and system design software - LabVIEW and WLAN toolkit. The programmable FPGA allows users to customize the instrument to their needs.


Figure 1


Figure 1 - The NI PXIe-5644R is ideal for implementing WLAN standards.

NI WLAN Measurement Suite

The NI WLAN Measurement Suite helps you perform common IEEE 802.11a/b/g/n/j/p/ac measurements with industry-leading speed and accuracy. Combined with high-performance multicore processors, PXI Express wireless local area network (WLAN) measurement systems can complete most 802.11 measurements five to 10 times faster than traditional box instruments. In addition, the WLAN Measurement Suite is compatible with 1-, 2-, 3-, and 4-channel PXI RF vector signal generators and analyzers as well as vector signal transceivers (VSTs).

The NI PXIe-5644R is the industry’s first vector signal transceiver (VST). Several models of the VST has been released since it's launch.  The VST features a 65 MHz to 6 GHz frequency range and up to 200 MHz instantaneous bandwidth. This instrument also features a programmable FPGA that can be used to speed up tests or implement real-time algorithms such as fast Fourier transforms (FFTs), power control, and even modulation or demodulation. This complete WLAN tester is three PXI Express slots wide and includes a programmable digital I/O port for device under test (DUT) control type of applications.


Benefits of a User-Programmable FPGA

The use of FPGAs with RF instruments is not entirely a new concept; however, the ability to provide users a programmable FPGA is new and unique to the NI VST. You can use the open FPGA for the following:

  • Servoing
  • Automatic gain control
  • Modulation and demodulation
  • FFTs and averaging
  • Channel emulation

A traditional boxed instrument restricts access to algorithms such as FFTs and even triggering. It can be difficult for a user to customize the FFT or triggering being used on a boxed instrument. However, the new era of software-designed instruments allows engineers to completely customize their instruments to their needs, much like customizing apps on cell phones. 

Traditional vs SW Designed

Figure 2 - Compare the software-designd approach of the VST with traditional approaches.



The VST coped with LabVIEW and the WLAN toolkit is the ideal instrument needed to implement the 802.11p standard because of its speed, performance, size, and flexibility. With the open architecture, users can customize the instrument all the way to the FPGA level, thereby enabling implementation of different standard. The VST combined a VSA and a VSG in one instrument. This will allow engineers to design and test the standard in one environment and using one system.