Design of wireless upgrade plan for AR1688 series VOIP phones
introduction
VOIP (Voice Over IP, voice service realized by sending IP data packets) is a technology that uses the Internet as a transmission carrier to implement voice communication between computers and computers, ordinary phones and ordinary phones, and computers and ordinary phones. VOIP voice communication technology has developed rapidly, and many new technologies are emerging. The H323 protocol we talked about in the past is now very old, and the MGCP transformed from H323 is to solve the problem from the perspective of traditional telecommunications, so product upgrading is the only way to track the development of VOIP. AR1688 series VOIP phones are developed on the basis of low-cost solutions, which have greatly improved the integration and performance compared to PA1688 series.
With the rapid popularization and development of 3G and WIFI networks, the application of wireless VOIP has also attracted more and more attention. The combination of VOIP voice communication technology and new wireless broadband will change the access and use of mobile and fixed voice services by enterprises and consumers. the way. This means that you can talk on the mobile phone network while walking on the street. After entering the office, the call can be seamlessly switched to WLAN voice technology. In a special environment where the mobile phone signal is weak, the software in the mobile phone will automatically transfer the call to the WLAN voice system, and when it is outside the WLAN coverage, the call will be switched to the mobile phone network. This article proposes a wireless upgrade solution based on AR1688 series VOIP phones.
1AR1688 VOIP phone system
Based on AR1688's VOIP phone system, its basic framework is to process complex speech encoding and decoding algorithms and network communication protocols. Among them, the speech codec algorithm requires a 100MIPS digital signal processor (DSP), which requires the use of high-performance processors in the design. At the same time, in order to realize the routing processing and forwarding of information, a network chip needs to be used in the circuit. In order to form a complete voice terminal, it must also include memory, power supply circuit, keyboard, display screen, power amplifier circuit, etc.
AR1688 VOIP phone system is composed of AR1688 main chip, network interface (1 ~ 2), Flash, power supply, keyboard interface and display interface. The block diagram of the AR1688 system is shown in Figure 1.
AR1688 is a programmable chip, 8-bit controller for VOIP protocol stack, and 24-bit DSP for voice compression algorithm. Compared with PA1688, AR1688 has higher performance, better voice quality and lower cost. AR1688 integrates 2 processors into one chip: 8-bit MCU is compatible with Z80 instruction set, the typical operating frequency is 24.576 MHz, and the maximum operating frequency is 60 MHz; 24-bit DSP uses ADI's ADSP2181 compatible processor, core computing power Up to 72 MIPS. Using DSP as the MCU coprocessor, internally solves the coordination problem of the two processors. Integrated on-chip 116 KB SRAM memory, no external SDRAM expansion required, maximum support 2 MB external memory, up to 4 external SRAM, EEPROM or Flash; integrated 18-bit high-quality CODEC on chip; integrated DC / DC conversion to provide core voltage; Support 24.577 6MHz crystal oscillator and on-chip PLL, support real-time clock; including 1 UART interface, 12 key keyboard interface, 16 general programming input and output interface (GPIO), simplifying system design and improving system stability.
At present, there are quite a few solutions for the wireless upgrade of the used wired network equipment, but nothing more than adding WIFI modules or TD modules to the existing VOIP products. This article adopts the method of installing WIFI module, and uses 88W8510 chip to realize wireless bridge to achieve the purpose of wireless upgrading of existing VOIP products.
2AR1688 VOIP phone wireless upgrade solution
In the VOIP telephone system, the VOIP phone is an indispensable component device. It is a user-end device for users to connect to the Internet network and provide users with various services. Although ordinary analog phones can be used as VOIP phones, the current development direction of VOIP phones is to realize voice compression coding, packet packaging, etc. by the terminal, and the terminal is directly connected to the Internet. The advantage of this is that it achieves all-IP communication, which can take full advantage of the various advantages of the IP network; at the same time, the terminal shares some of the functions of the gateway, making the network function configuration more flexible, which is the traditional wired design method. The idea of ​​this upgrade plan is to use the VOIP voice terminal designed based on the AR1688 chip, which is cost-effective, and uses the 88W8510 chip to realize wireless bridge connection and wireless access to the Internet to achieve the purpose of wireless upgrade of the VOIP voice terminal.
The 88W8010 WIFI module of the American Marvell company is a wireless bridge device that implements IEEE 802.11b / g functions. It solves the problem of upgrading traditional VOIP devices from wired to wireless registration to a SIP server. The specific solution is shown in Figure 2.
In Figure 2, the dotted line is the connection of the traditional LAN line to the Internet. After the 88W80lO WIFI module bridge is adopted, the VOIP device is connected to the wireless AP router through it, and then registered to the SIP server through the Internet.
3 AR1688 VOIP phone wireless upgrade hardware design
3.1 Features and advantages of 88W8010
88W8010 uses 2.4 GHz ISM frequency band; integrates all RF analog baseband transceiver functions; high-performance heterodyne RF structure; high linear built-in power amplifier with 23 dBm and antenna with transmit power of 20 dBm are connected to 802.11b and 802.11g, respectively; For the actual power detection, the transmission power cycle control function is integrated; a high-sensitivity receiver is used; a low-power design and an advanced power management mode; the 48-pin QFN package is only 7 mm × 7 mm in size.
The advantages of 88W8010 are: a single chip supports all RF to analog baseband functions and the IEEE 802.11g / b standard; it reduces material costs, simplifies board-level wiring design, and provides the smallest installation size, improving performance and omitting sound The use of surface bandpass filters reduces the cost; it can provide the antenna with a resolution of 0.5 dBm, 0-20 dBm transmit power; even if the specified parameters exceed the rated temperature, the power supply voltage and device parameters have changed. The output power of the device is also very stable; improve the detection method of weak signals and expand the detection range; provide low power consumption characteristics for device transceiver, sleep and energy-saving modes; compact hardware design, reducing space size.
3.2 Features and advantages of 88W8510
88W8510 built-in embedded ARM946S-E processor core; built-in antenna uses diversity receiving technology; for WEP and 80211i AES encryption and CCM information authentication, built-in hardware encryption engine; supports 802.11eQoS quality service guarantee; optional MII or PCI external interface ; Integrated 10 / 100M fast Ethernet MAC and PHY interface using VCT technology; support 802.1X security port protocol for advanced security certification; 256-pin TFBGA package, size meter 17 mm × 17 mm.
The advantages of 88W8510 are: 88W8510 chipset is an 802.11g solution and is compatible with 802.11b protocol; large reception range, good connection robustness, reduced information loss; high transceiver performance and wide range; based on low-power design It integrates as many functions as possible; it can connect more wireless terminals at the same time without reducing the wireless throughput performance; it can guarantee the continuity and stability of the transmitted data, audio and video data; it can be connected with multi-port routers and external systems Bus; Provide connection cable fault diagnosis method; To improve the security in public environment, add more identity certification agencies; Pin compatible with Marvell products using 802.11b protocol AP and gateway chip, convenient 802.11b and 802.11g Switching between.
3.3 Hardware design
The schematic diagram of 88W8510 WIFI bridge is shown in Figure 3.
The VOIP voice terminal designed based on the AR1688 chip is connected to the wireless AP router. The most critical one is the WLAN 802.11g / b-based AP and gateway chipset composed of 88WS010 and 88W8510. The combination of 88W8510 and 88W8010 chips is a cost-effective 802.11g interface. In-point / gateway solutions eliminate external CPUs and Fast Ethernet ports used for wired infrastructure connections, greatly reducing overall costs. The WLAN internal structure of the chipset is shown in Figure 4.
4 AR1688 VOIP phone wireless upgrade software design
Marvell provides the following support for customers using the 88W8510 chipset: board-level design reference; board-level firmware Bootloader design; related software design; diagnostic tools; SDK running in eCos and μClinux environment.
The operating environment is as follows:
System environment eCos
CPUARM946S-E
Debug interface JTAG
Development tool Marvell AP31_SDK_2.19S or above
The structure of the software solution is shown in Figure 5.
The functions of the product are as follows: 802.11g / b scanning; SSID network settings; WPA / WPA2, WEP (128-bit) / WEP (64-bit) security mode parameter settings.
Conclusion
This solution uses the programmable chip AR1688, and 88W8010 and 88W8510 WIFI chipsets to realize the wireless upgrade of VOIP phones. After actual testing, the terminal can achieve error-free communication within 40 m, with excellent call quality, stable operation, flexibility and convenience. Compared with similar solutions based on other technologies, this solution has the advantages of low cost and low power consumption.
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