MT9171/72, MT9173/74 Digital Network Interface Circuit (DNIC) DSL Modem Features & Benefits Guide. April 1999, Revision 1.0

Transcription

1 MT9171/72, MT9173/74 Digital Network Interface Circuit () DSL Modem Features & Benefits Guide April 1999, Revision 1.0

2 Summary Mitel s Digital Network Interface Circuit () Modem Single-chip devices capable of providing high speed, full duplex transmission up to 160 kbit/s over a twisted copper wire pair Selectable full duplex transmission at 80 or 160 kbit/s over single twisted pair ISDN compatible (2B+D format) using proprietary bi-phase coding MT9171 and MT9173 are designed for 3km loop length, while MT9172 and MT9174 are designed for 4 km loop length Provide Receive Synchronization pulse needed for loop delay measurements in wireless applications (MT9173 and MT9174 only) Offer Frame Synchronization and Clock extraction in all four devices. Low power devices (typically 50mW), single 5V supply Available in the following packages:22 Pin PDIP (MT9171/72), 24 pin skinny PDIP (MT9173/74), 24 Pin SSOP (MT9171/72/73/74) and 28 Pin PLCC (MT9171/72/73/74) -40 to +85 C temperature range Available now! Features and Benefits Support the 2B+D channel format (two 64 kbit/s B-channels and one 16 kbit/s D-channel) Provide a bidirectional interface between the Data/Voice (DV) port and a full duplex line operating at 80 or 160 kbit/s over a single pair of twisted pair wires Provide a line interface for implementing smart telephone sets with data and voice capability Can connect large numbers of terminals within existing computer networks Same device can be used for either master or slave operation Provide very low cost per line for terminal to computer links MT9174 provides designers with a simple method of measuring loop delay, which can be used to achieve the air-interface synchronization necessary for roaming Easy to implement with an off-the-shelf solution Low power consumption improves thermal management, system cost and reliability High functionality with minimal or no external support circuitry Page 2

3 Applications High Speed Internet/Data Access DSLAMs, Routers and Gateways for Multiple Tenant/Dwelling Units (MTU/MDUs) Digital PBX and Key Telephone Systems Wireless PBX Adjuncts and Controllers SOHO/ROBO CTI, Automatic Call Distribution (ACD), and Interactive Voice Response (IVR) Systems Commercial Aircraft Passenger Communications Systems Trading (broker) Communications Systems Apartment Security Systems Page 3

4 What is it? The is a low cost, single chip DSL modem that provides 80kbit/s or 160 kbit/s full duplex digital voice and data transmission over a single twisted copper pair. Introducing the new s! While customers were pleased with the ability of our MT8971/72 Digital Subscriber/Network Interface Circuit, many indicated the need for a low cost version and one optimized for wireless applications where there is a need for Frame Synchronization Marker Pulse. Mitel has developed the MT9171, MT9172, MT9173 and MT9174 specifically for these applications with improved cost and power consumption. How are the MT9173/MT9174 positioned in the market with the MT9171/MT9172? The MT9173 and MT9174 are well suited for Wireless Adjuncts and Controllers that require accurate synchronization between microcells. The MT9171 and MT9172 are intended for applications such as digital PABX linecards, telephone sets and in-building data distribution. What kind of applications can the new s be used in? High Speed Internet/Data Access DSLAMs, Routers and Gateways for Multiple Tenant/Dwelling Units (MTU/MDUs) Digital PBX and Key Telephone Systems Wireless PBX Adjuncts and Controllers SOHO/ROBO CTI, Automatic Call Distribution (ACD), and Interactive Voice Response (IVR) Systems Commercial Aircraft Passenger Communications Systems Trading (broker) Communications Systems Apartment Security Systems Page 4

5 Designer Benefits The MT917x series of s is ideal for providing interfaces at the ISDN basic rate (2B+D) using proprietary biphase line code. The high bandwidth and long loop length capability allows the s to be used in a wide variety of applications such as in smart telephone sets, Wireless Base Stations and in-building data distribution. Cost Space Tradeoffs Compromises Time-to-Market Low Power Functionality Fast Time-to-Market Low Cost High Functionality Low power Less Space Single chip off-the shelf solution Much lower cost than existing ISDN basic rate interfaces and TCMbased interfaces Full duplex transmission over twisted pair with a higher line rate (160 kbit/s) Extremely low power (typically 50 mw); it is suitable for linepowered applications such as digital telephone sets and high density DSLAMs Available in 24-pin SSOP packages that occupy 50% less area than equivalent PLCC and SOG packages Page 5

6 Key Features and Benefits Features Echo canceller-based full duplex transmission over a single twisted pair Selectable 80 or 160 kbps line rate Selectable master and slave mode Up to 3km or 9.8kft (MT9171/73), and 4km or 13.1kft (MT9172/74) Transparent modem mode capability Mitel ST-BUS compatible Low power, 50mW typical Available now in 24-SSOP, 24 - PDIP and 28-PLCC Digital output pin indicating the temporal position of the SYNC bit of the biphase transmission (MT9173 and MT9174 only) Benefits Echo cancellation technology allows % longer loop lengths versus half-duplex TCM (Time Compression Multiplex) schemes operating at the 160 kbit/s ISDN rate. Echo cancellation technology uses half the spectral bandwidth of TCM schemes thereby lowering EMI. s operate at speeds up to ISDN basic rate making them suitable for telephony and data transmission applications. Same device is capable of either master or slave operation, which maximizes economies of scale and simplifies sourcing logistics. Long loop reach makes them suitable for almost any inbuilding application. s can be used as a modem at the 80 or 160 kbps rate making them suitable for basic rate DSL applications such as high speed Internet access. s easily interface to PCM highways including Mitel s ST-BUS facilitating connection to Mitel s family of digital telephony components. Low power at 50mW (up to 35% lower than existing TCM schemes) reduces cost and maximizes system reliability. SSOP package occupies 50% less area than 28-PLCC and 24-SOG packages thereby doubling board density. SSOP package is low profile with 2mm height, which allows backside board mounting and increases board density. The MT9173 and MT9174 provide designers with a simple method of measuring loop delay. Loop delay can be used to achieve air-interface synchronization, which is necessary for roaming in mobile applications. No other chip on the market offers the features necessary to perform loop delay measurements. Page 6

7 Key Features and Benefits (cont d) Features Can adapt to continuously changing line conditions Transmit an extra housekeeping bit Status register contains two channel quality bits, which represent the quality of the data on the line Loopback mode allows the customer to perform in-system diagnostics Benefits Customers can change loop length or bridge taps and not have to do anything special for the to adapt. Customers can use this bit for anything they want. This feature can be used as a diagnostic tool. This feature can also be used as a diagnostic tool. Page 7

8 How is it used? Multiple Dwelling/Tenant Unit (MDU/MTU) Application The MT917x can be used in MDU/MTU applications for in-building distribution of high speed data on standard copper telephone wire pairs. High speed data from the Wide Area Network (WAN) feeds a Digital Subscriber Loop Access Multiplexer (DSLAM) usually located in the basement of the building. From there the DSLAM distributes high speed Internet data to routers or gateways located in each office or residence in the building. The maximum data rate achieved by the MT917x is 160 kbit/s is more than 3 times faster than today s 56K modems and the same data rate as basic rate ISDN. The MT9171 has a reach of 3km or roughly 10kft, which is satisfactory for most buildings. If further reach is needed, the MT9172 can be used for a reach of 4km or roughly 13kft. Use MT9171 Modem Inside Router and DSLAM Office Building Router Ethernet Router Ethernet Transmission Router Ethernet Router Ethernet WAN/MAN Intranet Internet Upper Floors DSLAM Basement T3/E3/T1/E1 Small PBX and KTS Figure 1 - Applications for Data Access Figure 2 explains how a small PBX or Key Telephone System can be constructed using Mitel products. A digital line card can be built by chaining or cascading many MT9171s or MT9172s together. The first (MT9171 or MT9172) receives a framing signal from the system and generates a delayed framing signal for the second MT9171 or MT9172. Each subsequent MT9171 or MT9172 in the chain accepts the framing signal output from the previous MT9171 or MT9172 and generates a delayed signal for the next in the chain. Mitel s integrated digital switch provides most of the PBX functionality and is useful for these applications. Page 8

9 MT9171 or MT9172 MT90812 IDX MT9161 CODEC MH88632 COIC MT8870 DTMF MT8843 CNIC MH88617 SLIC MT9161 CODEC MT8952B HDLC Microprocessor Figure 2 - MT9171/72 in PBX/KTS Applications Base Station using MT9171, MT9172, MT9173 and MT9174 Figure 3 shows the use of our new s in quad channel Base Station applications. The MT9171/MT9173 combination can be utilized in areas where 3 km reach is needed, whereas the MT9172/MT9174 combination can be used in areas where 4 km reach is required. Other Mitel products such as our new integrated digital switch (MT90812-IDX) can be utilized to perform functions such as switching. Mitel s quad ADPCM (MT9126) can be used for speech compression purposes. For superior speech quality use our state-of-the-art Acoustic Echo Canceller, the MT9315. Page 9

10 MT9160 Codec MT9315 AEC ADPCM Encoded Speech PBX Digital Phone MT9171 Wireless Access Controller ST-BUS MT9173 MT9126 Quad ADPCM Up to 3km MT9171 Four Channel Base Station Up to 3km MT90812 IDX MT9171 HDLC PLL ST-BUS ST-BUS MT9126 Quad ADPCM ADPCM Encoded Speech T1/E1 Framer T1/E1 Framer MT9174 Up to 4km MT9172 Four Channel Base Station Figure 3 - MT9171/72/73/74 in Base Station Applications Page 10

11 Wireless Local Loops Wireless Base Stations are common applications for the MT9171/72. Base Stations are usually located on rooftops, telephone poles, or ceilings in buildings. In many cases the Base Station connects to a centrally located access controller. Mitel s MT9171 and MT9172 provide excellent low-cost line interfaces for this application. If the Base Station must connect to a PBX or central office switch via a primary rate interface, the designer can choose from Mitel s family of framers and transceivers to make T1 or E1 connections. Network echoes in combination with framing delays in the system produce objectionable echo distortion. The MT9300 used for echo cancellation in the Base Station removes network echo, resulting in high quality voice. Twisted pair connecting to the network carries echo to the basestation MT9171/ MT9172 Line Interface MT9122/23, MT9300 Voice Echo Canceller MT9125/26 ADPCM Transcoder Base-band Processor Microprocessor Figure 4 - A typical DECT/PHS/CT2 Wireless Application Page 11

12 Wireless Access Controller Using the MT9173 or the MT9174 In the case of mobile phones, the frame synchronization between adjacent Base Stations must be closely aligned to ensure that calls are not dropped during handovers and that the transition is noise free. The MT9173 and MT9174 are particularly suited to wireless applications that require cell synchronization. The MT9173/74 s outperform all other products on the market. The receive synchronization bit, RxSB, allows very simple implementation of automatic loop delay measurement at any time. This information can be used to program a Base Station Controller delay circuit to compensate for various loop delays and allows a smooth handover, as shown in Figures 5 and 6. Base Station Controller Base Station 1 MT9174 MT9174 Loop3 Loop2 MT9172 MT9172 Hand over areas MT9174 MT9172 Loop1 Base Station 3 Mobile phone Figure 5 - MT9173/MT9174 in Wireless Base Station Controller Page 12

13 MT9173 and MT9174 Advantage The MT9173 and MT9174 are the only devices on the market that offer the features necessary to perform loop delay measurements. As a result, any digital system designed with MT9173 and MT9174 will offer significant cost savings during system installation and maintenance. The system will automatically calibrate the loop delay compensation circuitry without the need for expensive test sets or skilled technicians. In typical wireless communications people have freedom to travel while communicating on their mobile handsets. As the mobile handset moves about a Base Station s operating area, signal strength is constantly monitored. If the level drops below a specified threshold, the handset will search out other Base Stations that can offer a stronger signal. Once located, the handset will then switch to the new Base Station. During this switchover time, frame synchronization is vital. If a misalignment of air-interfaces exists due to different line lengths between Base Stations and the Base Station Controllers, then the channel will be momentarily corrupted, resulting in a audible cracking sound or a dropped cell. The MT9173 and MT9174 s RxSB pin allows the measurement of loop delay between the Base Station and the Controller. These measurements can be used to program a Base Station Controller delay circuit to compensate for various loop delays and allow a smooth handover. Wireless Access Controller From Base Station From Base Station From Base Station MT9174 or MT9173 MT9174 or MT9173 MT9174 or MT9173 DSTi DSTo RxSB DSTi DSTo RxSB DSTi DSTo RxSB Delay Circuit STo0 STi0 STo1 STi1 STo2 STi2 MT8980 Digital Switch Receive Synchronization Pulses RxSB RxSB RxSB Loop Delay Timer Circuit Microprocessor Figure 6 - MT9173 and MT9174 in Wireless Access Controller Page 13

14 Typical Questions and Answers Can I extend the loop length of the by using a bit rate of less than 80 kbit/s? Yes. Reducing the bit rate will marginally increase the loop length, although the MH89726 loop extender is a better solution. The is designed and evaluated for higher rates (80 kbit/s to 160 kbit/s). What is the correlation between the value of the CHQual bits and the bit error rate? The relationship between BER and the value displayed by the CHQual bits has not been characterized. Different devices may produce different results. These bits are meant to provide a qualitative indication of channel quality and should not be used to accurately determine BER. How can I frequency lock the MHz clock, required by the master, to C4b? There are two ways to do this: 1) Generate C10 from C2o by using a x5 frequency multiplier 2) Divide a MHz clock by 2,5 and 512 to produce C10, C4 and Fo respectively. Technical Notes are available upon request. Can the operate with a MHz data stream? No. The internal operation of the is set up to work with a MHz data stream such as an ST-Bus data stream. Operation with a MHz network would only be possible if an interface were available to reformat the MHz data into MHz format and a MHz clock source were provided. What effect do bridge taps have on system performance? The effect of the bridge taps depends largely on their location in the network. If they are in the transmitter/receiver, then the effect could be severe. The length of the bridge taps is also of concern. The most severe bridge tap is of the quarter wave length (around 250 meters). How does a transmit information in the modem mode? The can be used as a high speed, limited distance modem. The samples the signal presented to its Di pin at the selected baud rate. This signal is converted to a Biphase signal and sent on to the line. At the far end, the decodes the Biphase signal and recreates the equivalent data pattern. What does the loop extender do? With the extender circuit, performance in the range of 42dB of cable attenuation can be achieved. This corresponds to 6km on standard 24 AWG telephone cable for 80 kbit/s and 5km for 160 kbit/s. Page 14