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AB9800 PMP Technical SUMMARY February 2008

AIReach® Broadband Point-to-Multipoint Microwave Radio Solution

AB9800 PMP Technical Summary

1.0 Introduction

Point to Multipoint (PMP) technology offers operators cost advantages over alternatives such as leased lines, needing less equipment and giving more options for managing capacity and expansion. With a PMP system, operators get a flexible and efficient transmission solution that will help them cope with growing demand for high capacity and the ability to support a mix of ATM, TDM, and Ethernet traffic. It will also give them the flexibility to expand the network cost-effectively. To increase transport efficiency, the PMP system offers features such as statistical multiplexing gain, dynamic adaptive modulation and dynamic bandwidth allocation, allowing operators to generate additional revenue with minor software updates to their PMP network. Additional features for Ethernet applications include 4 types of QoS, VLAN support, VLAN tagging / untagging, and the ability to terminate Ethernet traffic into the core network as ATM, TDM, or keeping it in Ethernet frame format. In summary, the Hughes AB9800 Point to Multipoint system is a scalable and effective solution that allows operators to cut costs and expand their network cost-effectively.

2.0 Mobile Cellular Backhaul With Point to Multipoint Microwave Radio

2.1 AB9800 PMP Technology

Now that WCDMA 3G and HSDPA/HSUPA networks are becoming more common, operators are looking for a cost-effective, flexible way to carry large volumes of backhaul data traffic. Point-to-Multipoint is the answer to that quest, offering the ability to anticipate future demand for high capacity, without heavy investment in new equipment and installation. Using statistical multiplexing, dynamic bandwidth allocation and dynamic adaptive modulation, PMP offers operators the chance to cut the capital costs associated with an expanding network, allowing them to service the needs of a growing number of data hungry subscribers. In urban and dense urban area networks where the distance between BTS/Node-B is relatively short (between 0.4 ­ 3 km), the high density of 2G/3G Hub Stations pose a tremendous challenge for the transport network. PMP is well suited to meet the demand for high capacity backhaul in urban areas and represents a more cost-effective solution than leased lines and more economical than Point to Point radio link solutions. The AB9800 PMP solution brings a high level of scalability, integration and interoperability to 2G/3G cellular Hub Station access, giving lower operational costs and a more reliable network. In addition, one of the key advantages of the AB9800 system is that it can be

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AB9800 PMP Technical Summary

managed under a common network management system through a north-bound OSS interface. The AB9800 EMS is already in use with the Nokia NetAct as well as NetCool OSSs. The AB9800 System supports ATM, TDM, and Ethernet transport. Transporting ATM, TDM and Ethernet traffic over the same backhaul network, using the same radio equipment, cuts network complexity, allowing the operator to carry GSM traffic over TDM, and UMTS traffic over either ATM or as TDM directly over SDH. For corporate applications, metro Ethernet services or leased line E1 services can also be carried on the same AB9800 platform (see Figure 2-1).

92 Mbps/ carrier

Corp. Clients Node-B BTS BTS and Node-B


Figure 2-1.



AB9800 PMP System

2.2 AB9800 PMP System Elements and Terms

A typical deployment of PMP would encompass a number of PMP Hub Stations that provide a broadband wireless footprint for the planned service area. Each PMP Hub Station would have one or more sectors with AB9800 radios called Hub Terminals and an optional built in ATM concentrator unit to consolidate ATM traffic from individual sectors. The Hub Station may have several sectors, and each sector consists of an AB9800 Hub Terminal (HT). Each HT operates on its own RF channel and provides service to one or more RTs on that channel. In the case of a multi-sector Hub Station, a combination ATM concentration unit Hub Terminal (ACU-HT) can be used to concentrate the traffic from the individual HTs to the transmission network. Using this built in ATM concentration functionality means there is no need for an extra ATM switch. For a TDM backbone network, an existing SDH Add-Drop-Multiplexer (ADM) can be connected directly to the HTs with NxE1 interfaces. Figure 2-2 shows the system overview for the AB9800 PMP system.

© 2008 Hughes Network Systems, LLC



AB9800 PMP Technical Summary






d i g T Ma i t d i l g i V Xs a o n t A t t a i TM 3 1 0 0











Figure 2-2.

AB9800 PMP System Overview

Each PMP Hub Station connects several RTs to the transport network through the PMP wireless links. The RTs provide the user interfaces of the PMP system, including E1-CES, E1-TDM, E1-ATM, E1-IMA, E3-ATM, STM-1 ATM, and Ethernet interfaces, all of which are supported with a full set of QoS levels. Customer traffic may include 2G, 3G, WiMax, WiFi, metro Ethernet, leased line ATM or TDM, etc. The Hub Station supports three modes, TDM, ATM and IP and can migrate from one mode to another without requiring an equipment upgrade to the HTs. In fact, the HTs can support several modes at the same time. The RTs are connected to the Hub Station through the air interface. The AB9800 system supports an air interface with three modulation options, QPSK, 16-QAM, and 64-QAM on the same carrier on a burst-by-burst basis. The Hub Stations are connected to the central office by a transport network that can be TDM, ATM, or Ethernet based, with an EMS/NMS residing at the central office to manage the entire network.

2.3 Hub Terminal (HT)

Each PMP Hub Station consists of several HTs. Each HT consists of one Indoor Unit IDU, one Outdoor Unit ODU and a sectorized antenna (see Figure 2-3). One HT is required for each 28 MHz RF carrier and supports triple modulation with a capacity of 92 Mbps. The sectors can be 90° or 180°, giving flexibility of deployment. Additional options are available to share two ODUs on a single antenna or to split the output of an ODU to

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AB9800 PMP Technical Summary

multiple antennas. The AB9800 PMP system supports 1:1 and 1:N redundancy at the Hub Station (see chapter 3 for more detailed discussion of hub station configurations).

Figure 2-3.

AB9800 Hub Terminal

Figure 2-4 shows the different IDU variants available for use as an HT.

Figure 2-4.

AB9800 HT IDU Variant

2.4 ATM Concentrator Unit (ACU-HT)

The ATM Concentrator Unit ­ Hub Terminal (ACU-HT) provides standard HT radio functionality (28 MHz RF channel with up to 92 Mbps capacity) as well as ATM concentration. The ACU-HT is used to consolidate traffic from different sectors to the ATM backbone network, removing the need for an ATM Switch or ATM cross connect. Traffic from one up to eight HTs (7 other HTs + traffic from the ACU-HT itself) is concentrated by the ACU-HT and placed onto a single STM-1 interface going to the core network. An alternate configuration can be used whereby traffic from six sectors is terminated on up to

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AB9800 PMP Technical Summary

two STM-1 network interfaces. See Figure 2-5 below for a photo of the HT-ACU IDU (the eight blue connectors are all STM-1o ports).

Figure 2-5.

AB9800 ACU ­ Hub Terminal

2.5 Remote Terminal (RT)

The Remote Terminal consists of an IDU, ODU, antenna, and interfacility cable (IFL). The antenna and transceiver can be separated easily to eliminate the need for repointing if an ODU needs to be replaced (See Figure 2-6).

Figure 2-6.

AB9800 Remote Terminal

Figure 2-7 shows various configurations of the IDU available for use at the RT.

Figure 2-7.

AB9800 RT IDU Options

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AB9800 PMP Technical Summary

2.6 AB9800 System Services

The AB9800 is a flexible platform for providing TDM, ATM, and Ethernet services for different applications. The system supports all three services simultaneously on the Hub Station as well as the Remote Terminal. Figure 2-8 below show all three starting with ATM, TDM, and then the Ethernet services. · · ATM: native ATM services as well as native ATM with IMA are supported at the RT and terminated on either the E3 or STM-1 interface at the HT TDM: CES (TDM converted to ATM) services are terminate on either the E3 or STM-1 interface at the HT. A special mode called `transparent' TDM service offers extremely useful capability because in this service any type of data (ATM, TDM, Ethernet, etc.) are taken end to end on the PMP system. E1 interfaces are used at the HT and RT for this service Ethernet: three options are available for carrying Ethernet traffic. All the traffic originates on the LAN interface at the RT and terminates on either the ATM interface (E3 or STM-1), TDM interface (E1), or on the LAN interface


Figure 2-8.

AB9800 System Services

2.7 Element Management System (EMS)

The EMS is a centralized database EMS that manages the AB9800 HTs and RTs. The EMS platform runs on a Sun WorkstationTM with the Sun SOLARISTM operating system and can interface to a higher level OSS or NMS using the northbound SNMP interface. A Graphical User Interface is available to the operator to simplify network management. The EMS supports full FCAPS functions (see Figure 2-9): · · · · · Fault Management: alarm and control of the network Configuration Management: services provisioning Accounting Management: reports Performance Management: measurement of system performance Security Management: operator accounts and logging

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AB9800 PMP Technical Summary

Figure 2-9.

AB9800 EMS Functionality

The AB9800 EMS also features an integrated SNMP agent which allows the EMS to connect to a higher level OSS as shown in Figure 2-10. At present the north-bound agent has been implemented and available for use.

Figure 2-10.

AIReach EMS OSS Capabilities

The EMS has truly advanced connectivity options to the PMP Hub Stations. Either inband (on the ATM interface) or out of band (Ethernet, ATM, or TDM) connectivity can be implemented as shown in Figure 2-11.

© 2008 Hughes Network Systems, LLC



AB9800 PMP Technical Summary

Figure 2-11.

AIReach EMS Connectivity to PMP Hub Stations

3.0 AB9800 Hub Station Configurations

The AB98000 Hub Station architecture is unique compared to typical PMP systems in that it is distributed. Each RF channel is supported by a separate radio called an HT, a self-contained unit consisting of an IDU, ODU and antenna. Each HT IDU has its own enclosure, power supply, and network interfaces, allowing for a scalable system where a one-sector hub can be deployed in a 1u chassis! An AB9800 start-up sector can be deployed very economically without taking up huge amounts of rack space. See Figure 2-3 for a complete one sector PMP Hub Station. As more capacity is required over the air, additional HTs are added linearly. Another advantage of the system is that the AB9800 supports simultaneous ATM, TDM, and Ethernet transport both at the Hub Station as well as the customer site (remote terminal). The following sections describe these capabilities in more detail.

3.1 AB9800 PMP Hub Station With ATM Connectivity to the Core Network

When the core network is ATM based, the AB9800 simplifies connectivity with the use of the ACU-HT. As an example, consider a PMP Hub Station with four sectors and 1:1 redundancy. Three sectors will be served by a normal HT while the fourth sector uses an ACU-HT. The ACU-HT will concentrate the ATM traffic from the three primary sectors as well as its own sector and output the total traffic on up to 2 STM-1 interfaces to the core network. The same configuration is duplicated for the backup sectors (3 normal HTs and one ACU-HT). A block diagram example of a 4-sector redundant Hub Station is shown in Figure 3-1.

© 2008 Hughes Network Systems, LLC



AB9800 PMP Technical Summary

HT- 4 Backup HT- 4 Primary HT- 3 Backup HT- 3 Primary HT- 2 Backup HT- 2 Primary ACU-HT- 1 Backup ACU-HT- 1 Primary Lan Hub (in-band network mgt)

10 BaseT LAN for network management

STM-1 connections between IDU's

Integrated ACU-HT with 8 STM-1 ports

Network interface STM-1

Figure 3-1.

Example of a 4-Sector Redundant Hub Station in ATM Application

The key to the carrier-class HT redundancy is the ability of the backup HT to monitor and test the entire transmit and receive path of the backup radio with the RTs of each of the primary HTs in its redundancy group, while the backup HT is offline. The backup HT transmitter is tested by transmitting a test burst in a special timeslot that is left idle by the primary HT. The RTs listen for this test burst and compare its signal strength and signal quality to the primary HT's transmissions. The backup must send the test burst in the correct timeslot and alignment to the primary HT. The timing alignment is achieved through a redundancy bus between the Primary and backup HTs. This testing of the backup equipment provides a high level of confidence that a successful switchover will occur. It also minimizes the disruption to services caused by switchover as it eliminates the need for the RTs to perform re-acquisition and time synchronization with the backup HT. Failure of the background test done by the backup HT sends an alarm to the EMS so that the operator can take action.

3.2 AB9800 PMP Hub Station With TDM Connectivity to the Core Network

Figure 3-2 shows a 4-sector AB9800 Hub Station with 1+1 redundancy that connects to a TDM core network. The E1s from the HTs are aggregated by the SDH add / drop multiplexer for transport onto the core network. One of the E1 lines from the Primary HT #1 is used for the network management connectivity.

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AB9800 PMP Technical Summary

E1 10 BaseT LAN

HT- 4 Backup HT- 4 Primary HT- 3 Backup HT- 3 Primary HT- 2 Backup HT- 2 Primary HT- 1 Backup HT- 1 Primary Lan Hub NxE1


Network interface Existing SDH ADM


E1 NM interface

Figure 3-2.

Example of a 4-Sector Redundant Hub Station in TDM Application

3.3 AB9800 PMP Hub Station With Ethernet Connectivity to the Core Network

Figure 3-3 shows a 4-sector AB9800 Hub Station with 1+1 redundancy which connects to an Ethernet core network. The Ethernet traffic from the HTs is connected to the core network using a LAN Hub, Ethernet switch, or a router. The network management data is also carried in Ethernet format.

E1 10 BaseT LAN

HT- 4 Backup HT- 4 Primary HT- 3 Backup HT- 3 Primary HT- 2 Backup HT- 2 Primary HT- 1 Backup HT- 1 Primary Lan Hub


LAN Hub, Ethernet switch, Router, etc.


NM interface

Figure 3-3.

Example of a 4-Sector Redundant Hub Station With Ethernet Connectivity

3.4 AB9800 in Multi-Service Application

The AB9800 PMP system is truly future proof. The RT and the Hub Station each have ATM, TDM, Ethernet interfaces, allowing simultaneous carriage of each type of traffic, no matter what the origin. See Figure 3-4 for a diagram showing this multi-service capability. In addition to managing all the different traffic, the system has advanced features such as: · Dynamic bandwidth allocation for even more efficient sharing of the physical air bandwidth

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AB9800 PMP Technical Summary

· · ·

Dynamic adaptive modulation so that the maximum capacity can be realized for most of the time Four level customizable QoS for ATM and TDM traffic VLAN support as well as VLAN and type of service based QoS for Ethernet traffic

Figure 3-4.

AB9800 PMP is a Multi-Service Broadband Wireless Platform

3.5 RF Capacity and Reuse

The AB9800 PMP system can operate on three modulations (QPSK, 16-QAM, and 64-QAM) on a single radio carrier. The three modulations are supported on the same RF channel on a burst-by-burst basis. The advantage is that the sector can support the range of QPSK and the capacity of 64-QAM, allowing the RF plan to be optimized for any given sector. An example of RF reuse patterns supported by the AB9800 system is shown in Figure 3-5.

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AB9800 PMP Technical Summary









4x28 MHz channels No reuse

4x28 MHz c hannels With 2x reus e

Figure 3-5.

Frequency Re-Use With the AB9800 PMP System

4.0 Capacity Requirements and PMP Transport Efficiency

The transport network must accommodate high peak rates (HSPA challenges of mobile operators) of more than 10.7 Mbit/s for each BTS. To increase transport efficiency, the PMP system offers features such as statistical multiplexing gain, dynamic adaptive modulation and dynamic bandwidth allocation, allowing operators to get more capacity from the transport network and thereby generate additional revenue with only minor software updates to the PMP network.

4.1 Statistical Multiplexing Gain

A standard ATM UNI interface at the hub site brings the advantages of statistical multiplexing gain or oversubscription of VBR connections. Oversubscription of a VBR connection can be advantageous in a star network topology (which is what Point to multipoint is). As illustrated in Figure 4-1 below, there could be wasted capacity on individual connections, but when there is a shared downlink the wasted capacity is available for other users.

Fixed resource allocation: No statistical multiplexing

Statistical multiplexing ­ more traffic in same bandwidth

Wasted capacity

Figure 4-1.


Free capacity to carry more traffic

Statistical Multiplexing of the Air Bandwidth

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AB9800 PMP Technical Summary

4.2 Dynamic Bandwidth Allocation

Traffic requirements for RTs within a PMP sector can vary with time. Unlike Point to point systems, which are designed to accommodate peak capacity rate per link, in PMP systems, network planning principles should be based on peak capacity rate per sector. So, each service on an RT would be guaranteed a certain minimum bandwidth and a DBA pool would be set aside for allocation to users as needed. By doing so, the air channel is utilized more efficiently since peaks can occur randomly and capacity would be given only when needed. Dynamic bandwidth allocation allows the sharing of air bandwidth resources across a PMP sector so that capacity can be assigned to RTs as they request additional bandwidth. The DBA capability is especially important for mobile operators as they start deploying HSDPA and HSUPA in their 3G networks. DBA can allocate additional capacity in each direction as needed by the 3G base station. As implemented in the AB9800 PMP system, DBA ensures that there is a minimum capacity available for each service and when peak demands occur, the DBA feature will allocate additional unused capacity to RTs in real time (see Figure 4-2).

Bandwidth for dynamic allocation across remote terminals for peak capacity


Excess provisioned bandwidth per link

Figure 4-2.

Dynamic Bandwidth Allocation

4.3 Dynamic Adaptive Modulation

Dynamic Adaptive Modulation (DAM) allows air capacity to be increased by taking advantage of favorable atmospheric conditions. This feature enables the use of higher order modulation (64-QAM) on links which may previously have been dimensioned for 16-QAM modulation. The criteria for triggering a change in modulation are configured using received signal strength information, BER and indications of signal quality. In essence, DAM strives to offer the highest capacity for most of the time. Based on deployed PMP network cases, it could be assumed that 25 percent of all PMP links in a dense urban network will be planned with a link budget using 16-QAM

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AB9800 PMP Technical Summary

modulation. Applying adaptive modulation on these links will result in an immediate capacity gain. In addition, since data traffic may have less stringent availability targets than voice, further capacity gains can be expected by using DAM on data only sites which may have previously used QPSK modulation. During downshifting of modulation, the capacity delivered at an RT will be reduced. To ensure availability of service for critical applications, DAM will only drop the capacity to those services which have been marked as low priority within the EMS. Those services marked as high priority will maintain their capacity even in case of modulation downshift. DAM as implemented in the AB9800 system takes care to make modulation adjustments only on those links where the links require it, leaving other links operating in higher modulation.

© 2008 Hughes Network Systems, LLC




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