Design of wireless upgrade scheme for AR1688 series VOIP phones

introduction

VOIP (Voice Over IP, voice service implemented by sending IP data packets) is a technology that uses the Internet as a transmission carrier to implement voice communication between computers, ordinary phones, and computers and ordinary phones. VOIP voice communication technology is developing rapidly, and many new technologies are constantly emerging. The H323 protocol that we talked about in the past is now very old, and the MGCP transformed from H323 solves the problem from the perspective of traditional telecommunications, so product upgrading is the only way to track the development of VOIP. The AR1688 series VOIP phones are developed based on low-cost solutions, and they have greatly improved in integration and performance compared to the 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. VOIP voice communication technology, combined with new wireless broadband, will change the way enterprises and consumers obtain and use mobile and fixed voice services. This means that when walking on the street, you can talk through the mobile network, and when you enter the office, the call can be seamlessly switched to WLAN voice technology. In special environments where the mobile phone signal is very weak, the software in the mobile phone will automatically transfer the call to the WLAN voice system, and when it is out of WLAN coverage, the call will be switched to the mobile network. This article proposes a wireless upgrade solution based on the AR1688 series VOIP phone.

1AR1688 VOIP Phone System

The basic framework of the VOIP phone system based on AR1688 is to process complex voice codec algorithms and network communication protocols. Among them, the voice codec algorithm requires a 100MIPS digital signal processor (DSP), which requires the use of a high-performance processor in the design. At the same time, in order to realize the routing and forwarding of information, a network chip needs to be used in the circuit. In order to form a fully functional voice terminal, it must also include memory, power supply circuit, keyboard, display screen, power amplifier circuit, etc.

The AR1688 VOIP phone system consists of the AR1688 main chip, network interface (1 to 2), Flash, power supply, keyboard interface and display interface. The AR1688 system block diagram is shown in Figure 1.

AR1688 is a programmable chip, with an 8-bit controller for VOIP protocol stack and a 24-bit DSP for voice compression algorithm. Compared with PA1688, AR1688 has higher performance, better voice quality and lower cost. AR1688 integrates two processors into one chip: the 8-bit MCU is compatible with Z80 instruction set, with a typical operating frequency of 24.576 MHz and a maximum operating frequency of 60 MHz; the 24-bit DSP uses ADI's ADSP2181 compatible processor, with a core computing power of up to 72 MIPS. Using DSP as a coprocessor of MCU solves the coordination problem of the two processors internally. The chip integrates 116 KB of SRAM memory, no external SDRAM expansion is required, and supports up to 2 MB of external memory, up to 4 external SRAM, EEPROM or Flash; the chip integrates 18-bit high-quality CODEC; integrated DC/DC conversion provides core voltage; supports 24.577 6MHz crystal oscillator and on-chip PLL, supports real-time clock; includes 1 UART interface, 12-key keyboard interface, 16 general programming input and output interfaces (GPIO), which simplifies system design and improves system stability.

At present, there are quite a few solutions for wireless upgrade of existing wired network equipment, which are nothing more than adding WIFI modules or TD modules to the existing VOIP products. This article adopts the method of adding WIFI modules and using 88W8510 chip to realize wireless bridging to achieve the purpose of wireless upgrade of existing VOIP products.

2AR1688 VOIP Phone Wireless Upgrade Solution

In the VOIP telephone system, VOIP phones are essential components. They are user-end devices that connect users to the Internet 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 implement voice compression encoding, packet packaging, etc. by the terminal, and the terminal is directly connected to the Internet. The advantage of this is that it realizes full IP communication and can fully utilize 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. This is a traditional wired design method. The idea of ​​this upgrade plan is to use a VOIP voice terminal designed based on the AR1688 chip, which is cost-effective, and use the 88W8510 chip to achieve wireless bridging and wireless access to the Internet, so as to achieve the purpose of wireless upgrade of VOIP voice terminals.

The 88W8010 WIFI module from Marvell 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 SIP servers. The specific solution is shown in Figure 2.

In Figure 2, the dotted line is the connection from the traditional LAN line to the Internet. After the 88W8010 WIFI module is used for bridging, the VOIP device connects to the wireless AP router through it, and then registers to the SIP server through the Internet.

3 AR1688 VOIP Phone Wireless Upgrade Hardware Design

3.1 Features and advantages of 88W8010

88W8010 adopts 2.4 GHz ISM band; integrates all RF analog baseband transceiver functions; high-performance heterodyne RF structure; high-linearity built-in power amplifier with 23 dBm power and antenna with 20 dBm transmit power connected to 802.11b and 802.11g respectively; for actual power detection, it integrates transmission power cycle control function; adopts high-sensitivity receiver; low-power design and advanced power management mode; 48-pin QFN package, size is only 7 mm×7 mm.

The advantages of 88W8010 are: a single chip supports all RF to analog baseband functions and IEEE 802.11g/b standards; reduces material costs, simplifies board-level wiring design, provides the smallest installation size, improves performance, omits the use of surface acoustic wave bandpass filters, and reduces costs; can provide the antenna with a resolution of 0.5 dBm and a transmission power of 0 to 20 dBm; even if the specified parameters exceed the rated temperature, the power supply voltage and the device parameters change, the output power of the device is also stable; the detection method of weak signals is improved and the detection range is expanded; low power consumption characteristics are provided for device transmission and reception, sleep and energy-saving modes; the hardware design is compact and the space size is reduced.

3.2 Features and advantages of 88W8510

88W8510 has an embedded ARM946S-E processor core; built-in antenna adopts diversity reception technology; built-in hardware encryption engine for WEP and 80211i AES encryption and CCM information authentication; supports 802.11eQoS quality of service assurance; optional MII or PCI external interface; integrated 10/100M Fast Ethernet MAC and PHY interface using VCT technology; supports 802.1X security port protocol dedicated to advanced security authentication; 256-pin TFBGA package, size meter 17 mm×17 mm.

The advantages of 88W8510 are: the 88W8510 chipset is an 802.11g solution and is also compatible with the 802.11b protocol; it has a large receiving range, good connection robustness, and reduces information loss; it has high transceiver performance and a wide range; it integrates as many functions as possible on the basis of low power design; it can connect to more wireless terminals at the same time without reducing wireless throughput performance; it can ensure the continuity and stability of transmitted data, audio, and video data; it can be connected to multi-port routers and external system buses; it provides a method for diagnosing cable faults; in order to improve security in public environments, more identity authentication agencies have been added; it is pin-compatible with the AP and gateway chips that use the 802.11b protocol in Marvell products, facilitating switching between 802.11b and 802.11g.

3.3 Hardware Design

The schematic diagram of 88W8510 WIFI bridge is shown in Figure 3.

The VOIP voice terminal based on AR1688 chip design is connected to the wireless AP router. The most critical part is the AP and gateway chipset based on WLAN 802.11g/b composed of 88WS010 and 88W8510. The combination of 88W8510 and 88W8010 chips is a cost-effective 802.11g access point/gateway solution, which eliminates the external CPU and fast Ethernet port for wired infrastructure connection, greatly reducing the overall cost. The internal structure of the WLAN of the chipset is shown in Figure 4.

4 AR1688 VOIP phone wireless upgrade software design

Marvell provides the following support to 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 environments.

The operating environment is as follows:

System EnvironmenteCos

CPUARM946S-E

Debug interface JTAG

Development tools Marvell AP31_SDK_2.19S or above

The structure of the software solution is shown in Figure 5.

The product implements the following functions: 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, as well as the 88W8010 and 88W8510 WIFI chipsets, to achieve wireless upgrades for VOIP phones. After actual testing, the terminal can achieve error-free communication within 40 m, with excellent call quality, stable operation, and flexibility and convenience. Compared with similar solutions based on other technologies, this solution has the advantages of low cost and low power consumption.