Automotive telematics has been considered the third generation of high-tech evolution in the automobile industry. The first generation of the automotive technology evolution was guided by the high compression ratio power; the second generation of the automotive manufacturing improvement was driven by the advancement of the microelectronics control technology; the current trend of automotive evolution is considered to be governed by the “connectivity.” The “connectivity” emphasizes a vehicle's ability, while in operation, to exchange the information with its environments. Examples include the availability of the live, valid and accurate mapping/routing and traffic information for driving security aid and safety aid, as well as the availability of entertainments and mobile internet for better user convenience and services. Although the Dedicated Short Range Communication (DSRC) standard has currently been adopted worldwide for the short range wireless communication development in most automotive electronics system, according to the US regulation published in October 2004, however, automotive manufactures and service vendors are allowed to use the other medias to provide short-range communication and warning system and the associated services.
Recently, collision avoidance and warning systems have gained their worldwide attention in automotive communication research and development projects for traffic safety enhancement. The current widely adopted technologies for enhancing automotive communication systems can be categorized into two major areas; the technologies for short-range information detecting and sharing for better inter-vehicle supporting, as well as technologies for global environmental information reporting for traffic safety enhancement.
The most commonly used technology for the short-range information detecting/sharing system is the development of Collision Avoidance Radars, which targets on compensating drivers' blind spots. Video cameras equipped in some vehicle models are also used for aiding drivers' generally lacking of timely critical response to the sudden change of the surrounding traffic conditions and also compensating drivers' blind spots to aid drivers take appropriate timely actions to minimize the risk of collision. The drawback of a short-range detecting and informing system includes its range limit of 200 meters, not being able to penetrate barrier objects like the preceding vehicles, and also cannot detect the surrounding traffic condition at corners. As a result, the collision avoidance effect cannot take place while vehicles are moving in high speed or under hazardous circumstances due to drivers' blind spots. From the boom marketing's perspective, exploring the existing systems to provide drivers sufficient information on surrounding environment should gain its major role in the technology development arena.
The current development of the global environmental condition reporting technologies, on the other hand, is based on the imaging telecommunication systems. With global-range traffic condition broadcasting to inform drivers of live, up to date and correct information for the surrounding traffic condition as well as the planned driving routing information. With the radio broadcasting system, the information provided by the existing systems is lacking of real-time and detailed oriented micro perspective, which, however, is extremely important for a short-rang information system to efficiently response to a time-critical condition by providing reliable live data for the immediate forward and backward traffic conditions. Since for accident prevention, the cost for data transformation and services is too high, the existing system is still mainly for global traffic improvement.
An existing inter-vehicle communication technology with the addition of automotive collision avoidance radar is mainly a vehicle-to-vehicle communication and ranging system based on spread spectrum technique.
This inter-vehicle communication system includes a spread spectrum forwarding radar installed on the front end of the vehicle, and a receiver/transmitter installed on the rear end of the vehicle. The forwarding radar is for collecting the relative distance of the preceding vehicle and passively performing the inter-vehicle communication with the preceding vehicle. The rear end receiver/transmitter does not have the radar detecting capability and cannot send out passive communication signals. The rear end receiver/transmitter, however, can receive the radar signal from the rear vehicle and perform half duplex inter-vehicle communication.
The aforementioned technique for inter-vehicle communication system using a distance detecting radar is detailed as follows.
Using radar for distance detecting: taking the forward radar as an example, the radar transmitter emits forward spread spectrum code signals to the preceding vehicle. The reflected signal from the preceding vehicle then feeds back into the forward radar. Using the known relationship between the emitting and returned signal spread spectrum codes as well as the delay time of the returned signal, the signal processing module on the radar can accurately calculate the distance of the host vehicle relative to the preceding vehicle.
Inter-vehicle communication: The spread spectrum inter-vehicle communication uses half duplex mechanism. With phase shift keying (PSK) modulation, the forward radar on the host vehicle digitizes and modulates the traffic information message into the spread spectrum radar signals and synchronously sends them out via the forward radar transmitter. The rear end of the preceding vehicle is also equipped a compatible receiver to detect the radar signal and synchronously perform demodulation and de-spread-spectrum signal to decipher the traffic information the host vehicle tries to convey. Not having the ability to issue passive transmission signals, the receiver on the rear end of the preceding vehicle modulates again the received message back into the received radar signal and reflects the signal back into the host vehicle to complete the half duplex inter-vehicle communication mechanism.
The pros and cons of this conventional spread spectrum based inter-vehicle communication system are as follows. A forward spread spectrum radar sends out the signals, which are digitized data via spectrum spread process. The reflected signals from the preceding vehicle are then fed back into the receiver of the host forward radar. With both spread spectrum code association analysis and synchronous demodulation mechanism, the dual functions of information detection and information transmission/exchange for vehicle collision avoidance can thus be accomplished. This approach has advantage of efficient interference suppression. The drawback, however, of this approach is that the synchronization mechanism is hard to achieve. Without complete spread spectrum signal synchronization, both of the aforementioned function goals are in vain.
Currently, the plan for the research and development projects for automotive warning and communication technology is to establish the vehicle-to-vehicle mobile networking, so that a vehicle can retain the operation safety even in disadvantageous conditions like heavy fogged, icy road, or even in traffic accidents. Vehicles in the future are to be equipped with wireless communication accessories, which enable each vehicle to perfume all functions of transmitting, receiving and mediating the warning messages. For example, the first vehicle, which detects a dangerous road condition, can transmit a warning message to the surrounding vehicles. Any vehicle which receives the warning message can then mediate the message and transmit and propagate the warning to a wider range.