The advantages of the WPAN-based voice communication system (VoWPAN) are analyzed, and the VoWPAN system applied in the oil well site is designed and developed. The system includes two parts: audio gateway and voice terminal, which can provide point-to-point and point-to-multipoint wireless voice communication between the audio gateway and the voice terminal.
Through the use of high-density packaged Bluetooth modules and integrated design, the size of the system is reduced. In response to the problem of short standby time of voice terminals, measures such as sleep mode, reducing the length of the scanning window, increasing the scanning interval, and closing the host interface were adopted to reduce power consumption. By separating the host and RF front end of the audio gateway, the design difficulty of the antenna is simplified, the cost is reduced, and the shielding effect in certain occasions is overcome. It adopts standardized Bluetooth communication protocol and can be compatible with ordinary Bluetooth products. After testing, the communication distance of the system can reach 100m. The system has been successfully applied to wellsite control in many domestic oil fields.
As a supplement and extension of existing backbone networks (such as the Internet, public telephone networks, and public mobile communication networks), the application of wireless personal area network (wireless personal area network, WPAN) technology is on the rise, and the WPAN-based voice communication system (voice) overWPAN, VoWPAN) has gradually become a new application. Through VoWPAN, people can seamlessly access the existing public switched telephone network (PSTN), use mobile phones for communication in indoor occasions such as homes and offices, but the transmission power is very small and only costs the fixed network. For fixed and mobile communication network operators, the introduction of VoWPAN can provide communication services for enterprises, shopping malls and home users through telephone services different from wired or public hive systems, thereby effectively expanding network coverage and improving market competitiveness.
As one of the key technologies of WPAN, Bluetooth (Bluetooth) has broad prospects for application to VoWPAN. This article regards Bluetooth as the main technology of VoWPAN. On the basis of referring to the Bluetooth voice application reference model proposed by the international Bluetooth professional group (special interesTIng group, SIG), it focuses on the application of VoWPAN in the wellsite wireless communication. The design and development of a new type of VoWPAN system, including its software and hardware structure and work flow; then analyze its performance, especially the current consumption of the system, and give a method to reduce power consumption; Finally, analyze the remaining problems and problems Future development direction.
Key technologies of VoWPAN
VoWPAN uses the universality and maturity of the PSTN network. In the home and business environment, by using the WPAN voice terminal, you can freely make free calls within the WPAN coverage or make local calls through the PSTN. Generally speaking, VoWPAN system should meet the following requirements:
1) The voice coding used should have a small delay. At present, the more common speech code modulation techniques include pulse code modulation (pulse code modulation TIon, PCM) and incremental modulation. In order to increase the dynamic range of incremental modulation and thus improve the signal-to-noise ratio, continuous variable slope delta modulation (CVSD) is commonly used. Tests have shown that CVSD performs better than PCM at the same information transmission rate. Even if its bit error rate reaches 4%, voice quality is acceptable.
2) It must be able to resist all kinds of interference existing in the WPAN environment. Frequency hopping technology uses orthogonal pseudo-random hopping patterns to avoid "collision" and has a strong anti-interference ability. However, in a decentralized system, it is impossible to have ideal orthogonal frequency hopping patterns, which results in two or more users sending signals on the same frequency slot at the same time, that is, a collision occurs. The collision probability varies with the number of networks in the system. Increase and increase. In addition, there are many systems using frequency hopping technology in the Bluetooth operating band.
3) The geometric dimensions should be strictly limited, while having a standardized interface, so that it can be easily integrated into existing voice terminal equipment (such as wireless walkie-talkies, cellular phones, etc.). In view of the typical application of this system is to wear the voice terminal on the user's head, its volume and quality have very strict requirements.
According to the above requirements, this system uses DELBM's DFBM-CF121 Bluetooth module, which integrates CSRBC02, PCM codec, Flash storage and crystal oscillator, and its size is only 10.5mm & TImes; 10.5mm × 2.0mm. The openness of the Bluetooth technical specifications ensures that device manufacturers can freely choose their patent agreements or commonly used public agreements to develop new applications on this basis. The voice communication system proposed in this paper is based on its core protocol, and develops control and management application programs for voice terminals and audio gateways.
The Bluetooth 1.1 standard specifies that the link used to transmit voice is a synchronous connection-oriented (SCO), which supports symmetric, circuit-switched, and point-to-point connections. At present, the Bluetooth 112 standard and the 210 standard add an enhanced synchronous connection-oriented (eSCO), eSCO is to add some extension mechanisms on the standard SCO link, so that the link can support more flexible data packets The format, the data content in the packet, the period of the time slot, and also allows the addition of synchronization bits. In addition, eSCO supports limited data retransmission, enhances the error detection and retransmission mechanism during synchronous transmission, and is very suitable for transmitting voice.
The frequency hopping sequence of Bluetooth is very long, and has strong anti-interference performance, which can greatly reduce the interference between different types of networks and the same type of network, which is conducive to voice services that require high synchronization.
In addition, SIG is also committed to developing new applications of Bluetooth in voice. SIG gave several reference models for Bluetooth voice applications as early as the release of the Bluetooth 1.1 standard, including cordless telephone profile (CTP), intercom profile (IntP), headset application model (head setprofile , HSP), vehicle hands-free application model (hand free profile, HFP), etc. At present, SIG has also proposed some new reference models for voice applications, such as the wide band speech application model (wide band speech, WB-Speech), which uses a 16kHz sampling rate and conforms to the Bluetooth 1.2 standard synchronous chain that supports error detection and retransmission mechanisms road. In addition, SIG has also continuously proposed new versions of the voice application model (such as HFP1.5, CTP1.2, IntP1.2, etc.), with higher connection speed, more effective error detection and flow control, and stronger synchronization capabilities .
Due to the advantages of Bluetooth technology in voice transmission, it will definitely become the key technology of VoWPAN.
Design and Implementation of VoWPAN Communication System
The principle of Bluetooth VoWPAN communication system is shown in Figure 1. The communication system adopts Bluetooth technology and takes the Bluetooth phone application framework as a reference. It fully utilizes the characteristics of Bluetooth voice quality, small size, low power consumption, low cost and strong anti-interference ability to achieve Wireless voice access system for point-to-point and multipoint communication. Among them, the voice terminal may be the Bluetooth voice terminal described herein, or may be an ordinary Bluetooth headset, a cellular phone with Bluetooth function, a notebook computer supporting Bluetooth function, and the like.
This article mainly introduces the voice communication system that has been successfully applied to the oil well site. This system is the application of VoWPAN technology on the oil drilling platform. The schematic diagram of the well site is shown in Figure 2. The entire system is centered on the driller control room on the drilling platform, and the communication range covers the derrick, power generation device, mud device and other facilities. Staff can talk freely in the coverage area. The application of VoWPAN is formed in the internal LAN of the well site. Due to the hands-free design, the staff does not even need to press the keys when using it, so it is especially suitable for occasions when it is impossible to answer by hand. If a telephone line is connected to the driller's console, simply add a phone processing module to the gateway side, and the staff in the coverage area can make a call through the driller's console.
Compared with the application of VoWPAN in homes and offices, the system has higher requirements in terms of size, energy saving and anti-interference. Therefore, the voice communication system of the wellsite described in this article can be applied to various occasions such as hospitals, homes, offices and so on.
In-ear Wired Earphones, they are small and comfortable and simple, fit in just about any pocket,and they provide great sound that literally goes straight into your ears,bring it on your next commute or run, or simply enjoy it in the comfort of your time.
In-ear Wired Earphones
Earbuds With Removable Cable,Earphones With Replaceable Cabl,Stereo In-Ear Earphones,In-Ear Wired Headphones
Dongguang Vowsound Electronics Co., Ltd. , https://www.vowsound.com