Airstar for Mobile Transmission Networks

airstar For Mobile Transmission Networks

WHITE PAPER 033-100458-001, ISSUE 1 2

Notice The information in this manual is subject to change without notice. All statements, information and recommendations in this manual are believed to be accurate, but are presented without warranty of any kind, expressed or implied. Users must take full responsibility for their use of any products. No part of this publication may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying and recording, or by any information storage or retrieval system, without prior written consent from SR Telecom Inc. SR TELECOM, AIRSTAR, ANGEL, INSIGHT NMS, METROFLEX, METROPOL, SR500, SR500IP, SWING, and WL500 are trademarks of SR Telecom Inc. All rights reserved 2004. All other trademarks are property of their owners. Information subject to change without notice. © 2004, SR Telecom Inc. All rights reserved. 8/30/04 Printed in Canada


Table of Contents

Introduction ............................................................................................................4 Version History.......................................................................................................4 Executive Overview ...............................................................................................5 Point-to-Multipoint Business Case .........................................................................7 Point-to-Multipoint Business Case .......................................................................11 airstar Access Network Components ...................................................................16


Introduction The airstar™ for Mobile Transmission Networks white paper, revision 1.1, was originally updated in November, 2003. Version History The version history for the airstar for Mobile Transmission Networks document is listed in Table 1.1. Table 1.1 Document Release History Date Version Description 5/7/02 0.1 Initial Draft

5/22/02 0.2 Completed the coverage and capacity sections

7/24/02 1.0 Updated the system overview sections per System Overview,

Revision 1.0

11/2003 1.1 Updated the system overview for the SAS-4000 enhanced

platform and removed the end-of-life (EOL) SAS-XP platform


Executive Overview With the impending deployment of third generation (3G) technologies in mobile networks, operators are faced with the challenge of upgrading their transmission and core networks to an Asynchronous Transfer Mode (ATM) technology for the efficient handling of voice and robust data applications. The transition to 3G technologies will require that greenfield 3G operators deploy completely new transmission and core networks that are designed from the start to use ATM technology. While existing 2G operators, upgrading to 3G technologies, will need to expand the capacity of their transmission networks to accommodate the addition of the 3G base stations to existing tower sites, as well as convert their core networks to use ATM technology. The expansion of capacity exceeds the capacity of existing point-to-point (PTP) microwave links and requires the rationalisation of operating expenses (OPEX) associated with leased E1 facilities. SR Telecom believes these two factors create opportunities for a point-to-multipoint (PMP) technology to play a significant role in 3G transmission networks. When compared on a total cost of ownership basis, PMP is the most cost-effective technology when five or more 2G or 3G tower sites can be reached from a single base station. Recurring operating expenses are also lowest with PMP technology due to the reduced dependence on leased E1 facilities, as well as the lower costs for roof rights due to the deployment of fewer antennas. This results in higher operating margins and higher stock valuation for a mobile operator. The role of airstar in mobile transmission networks is shown in Figure 1.1. Within a metropolitan area of coverage, the PMP base stations are distributed throughout the metropolitan area and interconnected with the Radio Network Controller (RNC) and the Mobile Switching Centre (MSC) through Synchronous Digital Hierarchy (SDH) fibre or Synchronous Transfer Module 1 (STM-1) point-to-point links. A single PMP base station at 26 GHz or 28 GHz can support a coverage range of up to 40 square kilometers, providing coverage to dozens of 2G and 3G tower sites. The base station can be configured with as few as two sectors to minimize base station entry cost or with as many as 12 sectors for high-density urban deployments, providing up to 672 Mbps of capacity. At each tower site, an airstar Subscriber Access System (SAS) provides the backhaul from the Node B or the Base Transceiver Station (BTS) to the PMP base station, shown in Figure 1.1. For the backhaul, the following interfaces are provided:

For 2G sites, a fractional E1 (FE1) interface can be provided to the BTS For low-capacity 3G sites, an Inverse Multiplexed ATM (IMA) interface is provided

over two E1 physical interfaces

For high-capacity 3G sites, an STM-1 ATM interface is provided For mixed 2G and 3G sites, two E1s and an IMA interface or four E1s and an

STM-1 interface can be provided from a single airstar SAS indoor unit


Executive Overview (cont’d) The airstar SASs also support a 10/100Base-T interface, enabling simultaneous backhaul for Wireless Local Area Network (WLAN) hotspots using 802.11b technology. Network timing can be taken from the SDH network and distributed to the Global System for Mobile Communications (GSM) BTS or it can be passed at the ATM layer using Synchronous Residual Time Stamp (SRTS) mode of the ATM Adaptation Layer 1 (AAL1) for cases where the SDH backhaul is leased from another operator. AirView™Link Navigator provides complete fault, configuration, accounting, performance, and security management for an airstar access network. Link Navigator is a carrier-class network management system (NMS) that can manage a nationwide airstar access network from a single network operation centre (NOC). The airstar network elements support plug and play capability, receiving their configuration and provisioning through the southbound Simple Network Management Protocol (SNMP) interface from Link Navigator. Integration with Element Management Systems (EMSs) for the radio access network and ATM core network is provided through Link Navigator over Common Object Request Broker Architecture (CORBA)-based northbound interfaces to support end-to-end provisioning and fault management applications. Figure 1.1 airstar Mobile Transmission Network


Point-to-Multipoint Business Case The competing point-to-multipoint transmission network technologies are leased E1 lines and point-to-point microwave links. In addition, all capital expense (CAPEX) and OPEX contributions need to be included to compare the different technologies on a total cost of ownership basis over a five-year period. Capital Costs The capital costs for an airstar PMP access network deployment are described in this section. Transmission Network CAPEX A primary consideration is the basic CAPEX of the PMP and PTP equipment. The PMP equipment incurs the fixed cost of the base station before any subscriber terminals are deployed. The entry cost of the PMP base station is a main factor in the cross point of the number of links between PMP and other technologies. Furthermore, since a single PMP base station sector serves multiple BTSs and Node Bs in the same geographic area, full redundancy is typically required to eliminate a single point of failure. To minimize entry costs, airstar offers an entry-level configuration for a PMP base station with two, 180° sectors. As demand for capacity increases, the base station can be upgraded to four sectors, doubling the capacity. The budgetary pricing for the PMP base station in this analysis is as follows:

• $74, 700 for a two-sector base station, fully redundant configuration • $143,900 for a four-sector base station, fully redundant configuration

The incremental costs for the PMP as Node Bs or BTSs are added to the hub site as part of the cost of the customer premise equipment (CPE) terminals. For PTP links, the incremental costs are two PTP terminals, one on each end of the link. Budgetary pricing for the CPE in this analysis is as follows:

• $5,000 for a PMP CPE • $14,000 for a PTP link, both terminals

Transmission networks based on E1 leased lines and PTP links provide pure layer 1 transmission from the Node B to the RNC. These networks rely on IMA to create the single logical ATM interface from many physical E1 interfaces. The IMA interfaces from each Node B are aggregated at the ATM core network onto an STM-1 facility to interface to the RNC. Therefore, for leased lines and PTP links, an IMA module is required at the core network for each Node B being backhauled. A market value of $5,000 is assumed for an IMA module. airstar provides integrated ATM access aggregation within the base station to provide an STM-1 trunk interface. The airstar SAS-XP provides the IMA functionality directly at the base station site. Therefore, the ATM core network does not bear any incremental CAPEX for the IMA aggregation function.


Point-to-Multipoint Business Case (cont’d) Incremental ATM Core Network CAPEX Transmission networks based on E1 leased lines and PTP links provide pure layer 1 transmission from the Node B to the RNC. These networks rely on IMA to create the single logical ATM interface from many physical E1 interfaces. The IMA interfaces from each Node B are aggregated at the ATM core network onto an STM-1 facility to interface to the RNC. Therefore, for leased lines and PTP links, an IMA module is required at the core network for each Node B being backhauled. A market value of $5,000 is assumed for an IMA module. airstar provides integrated ATM access aggregation within the base station to provide an STM-1 trunk interface. The airstar SAS-XP provides the IMA functionality directly at the base station site. Therefore, the ATM core network does not bear any incremental CAPEX for the IMA aggregation function. Site Acquisition Costs The airstar CPE is as easy to install as a direct satellite receiver. A service technician installs the SAS inside a mobile cabinet or shelter, applies power, and connects the coaxial cable to the Subscriber Radio Unit (SRU). The SAS also supports plug and play capabilities, requiring no command line interface configuration. To facilitate alignment, the SRU provides an received signal level (RSL) indicator voltage directly through a BNC connector, which can be measured using a digital multimeter. Portable spectrum analyzers or sophisticated field installation tools are not required. When a RSL voltage peak is detected, the SAS will have already been admitted into the network and provisioned by the base station. Since installation services in many cases are outsourced by a wireless operator to a third party professional service provider, the plug and play installation of the airstar CPE allows the operator to use the same low-cost installation service companies that provide the same services for direct satellite operators or cable modems. Installation costs are typically under $500 per CPE. The installation of the base station, while not as plug and play as the CPE, is still straightforward. The base station radios are sectorized and aligned using a compass. With one visit to a site, four or eight radios for two-sector or four-sector configurations, respectively, are installed simultaneously. A menu-driven craft interface allows a service technician to initially configure a few parameters on the base station to establish communication with the NMS. From the NMS, the base station then downloads its configuration and ATM service provisioning. The installation of the indoor portion of the airstar base station is comparable to the installation of a point-to-point link. Complete base station installations can be achieved with a single truck roll for less than $5,000.


Point-to-Multipoint Business Case (cont’d) Site Acquisition Costs Each link of a PTP system is more difficult to install, since both sides of the link must be aligned and configured simultaneously. Aligning the link requires a service technician at each end of the link to coordinate access with each site owner. Each end of the link is alternatively and iteratively aligned until the RSL indicators at both ends measure a maximum level. The service technicians must be in constant communication to determine which end of the link is misaligned. After the radios are aligned, the indoor units are manually configured with all of the port settings, and each end must wait for the other to finish before verifying that the link is passing traffic. This process is time-consuming, requires two people per link, and can take twice as long as a PMP installation. The site acquisition costs of PMP and PTP links for various numbers of Node Bs or BTSs per hub site are shown Figure 2.1. Since the minimum number of radios at a PMP base station for a two-sector, redundant base station configuration is four, comparing the PMP and PTP at this operating point, shows that PMP installation costs are lower. The higher installation costs for the PTP links easily overtake the one-time fixed installation costs of the PMP base station, with only a few number of links at the hub site. Figure 2.1 PMP and PTP Site Acquisition Costs


Point-to-Multipoint Business Case (cont’d) Operating Expenses The long-term valuation for mobile operators is based on the operating margin, and operators that achieve higher operating margins are rewarded with higher stock valuations. The ongoing costs of leased backhaul can represent one of the largest operating expenses; and as a result, one of the largest drags on operating margins. Leased Facilities As the capacity of a transmission network, based on leased E1s, increases to accommodate the deployment of 3G base stations, the associated operating expense increases by 300%. A GSM BTS can require as little as a 384 Kbps FE1 for backhaul; however, a 3G Node B requires two E1s of traffic for urban and suburban deployments, and up to five E1s in densely populated urban environments. Even if a mobile operator can obtain leased E1 lines for as little as $300 per month from the tower to the Local Exchange Carrier (LEC) central office, this still represents upwards of $1,000 per month per combined 2G and 3G tower site. There are likely to be multiple hub sites for PMP and PTP, which require backhaul to a mobile switching centre. These will typically use STM-1 fibre facilities. In the case of leased lines, backhaul will also be required from the LEC's central office to the mobile operator's switching centre. This part of the backhaul facilities is constant across all three access technologies. The incremental costs for E1 to STM-1 aggregation for leased lines has already been discussed in Section 2.1.2 “Incremental ATM Core Network CAPEX”. Roof Rights Many mobile operators have removed tower properties from their balance sheets, choosing to lease them back from the tower aggregators. While this has the benefit of allowing the wireless operator to gain access to the rest of the tower aggregator's portfolio of properties, the mobile operator must now pay a monthly lease, or roof right, for each antenna installed on the tower site. The roof rights can even be based on antenna diameter to discriminate between short-haul and more expensive long-haul links. Typical roof rights are $100 per month per foot of antenna diameter, or $200 per month for a two-foot antenna. The PTP systems incur fixed roof rights for four or eight antennas at the hub site for two-sector and four-sector redundant configurations, respectively. However, the incremental roof rights for each link deployed is for a single antenna. The PTP systems will incur roof rights for each end of the link; and as a result, will have twice the incremental roof rights as a PMP system.


Point-to-Multipoint Business Case Spectrum Costs In many countries, 3G license holders are being awarded spectrum at 28 GHz for close to nothing, provided that the spectrum is used for their own backhaul purposes and not for access applications. The spectrum auction for 28 GHz in the United Kingdom (UK) resulted in negligible bids for the top-tier cities and no bids for other regions. A re-auction by the UK regulator has resulted in no new bids after two months. In other countries with new spectrum allocations, the spectrum is being allocated on a beauty contest basis with minimal financial requirements. In addition, the spectrum licenses of many fixed wireless Competitive Local Exchange Carriers (CLECs) who were unable to gain their next round of funding can be acquired for pennies on the dollar.

The cost of spectrum is not considered significant to the business case.

In this analysis, it is assumed that the mobile operators have acquired a spectrum license on a region-wide basis that allows them to deploy either a PMP or PTP technology. There is no per link license fee associated with PTP.


Point-to-Multipoint Business Case (cont’d) Total OPEX The relative OPEX for PMP, leased lines, and PTP technologies is shown in Figure 2.2. With three E1s required for each Node B site, leased lines have the highest operating costs compared to the PTP and PMP technologies. Looking at the operating point of four links per hub site, the PMP technology has lower operating costs than the PTP, dominating the other two technologies for more than four links per hub site. The discontinuity in the slope for the PMP technology at 10 links, shown in Figure 2.2, is due to an expansion of the PMP base station from two to four sectors. The PMP technology results in the lowest recurring operating costs for a mobile operator and the highest operating margins. Figure 2.2 Relative OPEX for Leased Lines, PTP and PMP Technologies


Point-to-Multipoint Business Case (cont’d) Total Costs of Ownership The total cost of ownership for a transmission network is defined as follows:

The CAPEX, including the incremental core network CAPEX and the installation costs

The present value of the OPEX, including the facilities leased and the roof rights, over a five-year period

The results of the previous sections are combined in Figure 2.3 to show this result. One expected result is that PTP has a lower cost of ownership than the leased lines. PMP also has a lower cost of ownership than leased lines for four or more links per hub site. When PMP is compared to PTP, the PMP technology has a lower cost of ownership for five or more links per hub site. The discontinuity in the slope of the PMP curve at 10 links, shown in Figure 2.3, is due to the expansion of the base station from two to four sectors. Figure 2.3 Total Cost of Ownership for PMP, Leased Lines, and PTP Technologies


Point-to-Multipoint Business Case (cont’d) Intangible Costs This section describes the intangible costs of an airstar access network. Unified Transmission Network Reduces OAM&P Costs By moving the majority of a 2G and 3G transmission network to a PMP technology with an ATM core network, operations, administration, maintenance, and provisioning (OAM&P) functions can be integrated. With leased lines, a mobile operator typically loses visibility on fault management and network performance, since the leased facilities are part of another operator's network. This results in longer times to isolate faults and resolve system performance problems, in addition to the lost revenue due to network outages. Reduced Dependency on Another Operator for Facility Maintenance With leased facilities, the mobile operator is dependent on a wireline operator, usually the LEC, for the maintenance of the facility. While contracts for leased lines stipulate service level agreements for service availability, the associated penalty clauses in the form of service rebates, rarely compensate for the lost service revenue due to a network outage. Greater Link Reliability Reduces Lost Revenue due to Service Outage Even when deploying a PMP or PTP technology, the mobile operator can still be dependent on a tower owner's technicians to replace a faulty unit. With PMP technology, half the link is configured for full redundancy; therefore, service is not affected when a base station radio encounters a failure condition. Since service is not affected, a failed base station radio can be replaced at the convenience of both the mobile operator and the tower owner. With PTP technology, a failure on either side of the link results in a service outage and lost revenue. The length of the service outage depends on the service level agreement with the tower owner that stipulates the response time by their technicians. The repair calls for a PTP link must be coordinated between the mobile operator’s technicians and the tower owner's technicians, since the mobile operator technicians are responsible for the replacement of the unit and the tower owner technicians are responsible for the installation of the unit.


Point-to-Multipoint Business Case (cont’d) Statistical Multiplexing Gains An airstar point-to-multipoint access network provides the opportunity to statistically multiplex gains in the air capacity through the use of real-time variable bit rate (rt-VBR) and non-real-time VBR (nrt-VBR) service classes. The preceding analysis assumed that both 2G and 3G services were being deployed as a constant bit rate (CBR) service class, and did not take advantage of the statistical multiplexing gains. This is consistent with the way many mobile operators view their initial deployments, where the focus is on network robustness. These initial deployments also provide mobile operators with the opportunity to develop traffic models for 3G services, which allows their mapping onto VBR service classes. By using rt-VBR service class for 3G traffic, there is the potential for perhaps a statistical multiplexing gain of 2:1, effectively doubling the capacity of the base station.

The Virtual Channel Connections (VCCs) carrying management and control plane traffic can be mapped to VBR service classes from the start.

Seamless Integration with WLAN Hot Spots Many mobile operators are including WLAN technology as part of their service offering to traffic hot spots, either as a data offload for General Packet Radio Service (GPRS) or to expand their 3G deployments in areas where they may not have 3G coverage. All airstar CPEs provide Fast Ethernet interfaces that can provide up to 8 Mbps of backhaul from 802.11B (IEEE standards for wireless LANs) access points.


airstar Access Network Components This section describes the airstar access network components. Coverage and Capacity An airstar access network using 4 QAM (quadrature amplitude modulation) operation for a 28 MHz channel scheme, provides 28 Mbps of net subscriber throughput for optimal coverage and capacity. The low Carrier-to-Interference (C/I) requirements of 4 QAM allows the same frequency set to be reused at the same base station, supporting the configuration of high-capacity, 12-sector base stations with as few as two frequency sets and two polarizations available. Table 3.1 airstar 26/28 GHz Range and Availability

ITU-R Rain Region Radio Family Link Availability E H K

99.99% 8.55 km 6.38 km 5.17 km ETSI 26 GHz

99.995% 6.93 km 5.15 km 4.16 km 99.99% 7.60 km 5.67 km 4.60 km

ETSI 28 GHz 99.995% 6.15 km 4.58 km 3.70 km

The traffic requirements and density of 3G deployments for suburban, urban, and dense urban environments expected for 2005 are shown in Table 3.2. In suburban environments, the spacing used for Node B is 2.3 km with a traffic demand of 3.5 Mbps, or less than 2 E1s. Mobile cells are hexagonal with a radius of half the Node B spacing. The PMP cells approximate a square with a diagonal of twice the range. Using the results listed in Table 3.1 for ITU-R rain region K with a 99.995% availability, the PMP base station has sufficient range to cover 10 suburban Node Bs for an aggregate traffic demand of 35 Mbps. Table 3.2 PMP Coverage and Capacity for 3G Deployment Scenarios

Description Dense Urban Urban Suburban

Node B Spacing (km) 0.4 0.8 2.3

Traffic / Node B (Mbps) 10 4 3.5

Node B / PMP Base Station 50 83 10

PMP Base Station Capacity (Mbps) 504.0 333.1 35.3

PMP Spectrum (MHz) 56 56 56

Capacity per Sector 31.5 31.5 31.5

Base Station Sectors 16 11 2

PMP Base Station Spacing (km) 2.8 7.3 7.3


airstar Access Network Components (cont’d) Network Timing Distribution The GSM networks require that the BTS be synchronized with the MSC, and that the timing passes through an E1 trunk. With PTP radios or SDH fiber, the timing for the physical E1 interfaces to the BTS can be taken from the MSC. The 3G networks, which use ATM in the transmission network, do not require synchronization of the Node B to the RNC, but merely the availability of a stable timing frequency reference for the radios. For 2G or combined 2G and 3G backhaul, a PTP system must also be able to pass timing for the E1 interfaces to the 2G BTS, shown in Figure 3.1. The PMP base station derives its timing from the SDH network and passes the timing to the SAS through the downstream symbol clock. The SAS synthesizes the timing for the E1 interface from this downstream symbol clock. In cases where the SDH fiber is owned by a mobile operator, leased dark fiber, or provided by STM-1 PTP radios, the timing of the STM-1 interface can be synchronized to the mobile operator’s clock. Typically, a mobile operator leases STM-1 tributaries within the SDH fiber facilities between the MSC and the PMP base station. In this scenario, the timing of the STM-1 trunk interface is synchronized to the SDH fiber operator's network clock, not the mobile operator's clock.


airstar Access Network Components (cont’d) Network Timing Distribution To recreate the MSC timing on the E1 interfaces presented to the BTS, the timing of the E1s needs to be carried at the ATM layer, since there is no E1 physical layer connectivity between the MSC and BTS. This is provided by using the SRTS mode of the AAL1. This mechanism carries timestamps for the E1s within the AAL1 overhead. Both the ATM core switch and the PMP CPE must support the SRTS to be able to pass the timing end-to-end. The SRTS is superior in jitter tolerance and sensitivity to cell loss to other ATM techniques, such as adaptive clocking. Figure 3.1 Network Timing Distribution Using SRTS Mode


airstar Access Network Components (cont’d) Subscriber Access System (SAS) The SAS is an indoor unit that is installed directly at the subscriber’s premises. The SAS provides the intermediate frequency (IF) interface to the Subscriber Radio Unit (SRU), the modem, and the ATM adaptation to the subscriber interfaces. 4000 Series SAS (SAS-4000) For backhauling 2G BTSs, the SAS-4000 presents the lowest cost option. It provides four E1 interfaces to connect to multiple 1G and 2G BTSs, as well as a synchronous serial interface that can be configured for X.21 or V.35 operation. The SAS-4000 also provides a 10/100Base-T interface supporting up to 10 Mbps throughput for backhauling WLAN hot spots. For mobile transmission applications, the SAS-4000 can provide two E1s for 2G backhaul applications and two E1s configured as an ATM/IMA interface for 3G backhaul applications. A 10/100Base-T interface is also supported for local management traffic or for backhauling 802.11B WLAN hot spots at rates of up to 10 Mbps. The SAS-4000 is housed in an 1-RU (rack unit) plastic enclosure that is mounted on a 19 inch rack, shown in Figure 3.2. The SAS-4000 supports 3.5 MHz channels at 16 QAM operations, 7 MHz channels at 4 QAM operations, 14 MHz channels at 4 QAM operations, and 28 MHz channels at 4 QAM operations.

Support for 4 QAM operations using 28 MHz channels on a SAS-4000 is under future consideration based on the requirements of 2G only, rather than combined 2G and 3G, backhaul.

Figure 3.2 SAS-4000


airstar Access Network Components (cont’d) 5000 Series SAS Ultra (Future) For higher capacity tower sites, SR Telecom™ plans to introduce in the future the 5000 Series SAS (SAS-5000) that will provide an STM-1 ATM interface to connect to 3G Node Bs, as well as four E1s to connect to 1G and 2G BTSs. For maximum flexibility, the four E1 interfaces can be configured in any combination for Circuit Emulation Service (CES) or IMA. The SAS-5000 will also provide a 10/100Base-T interface that can be used for 802.11B WLAN backhaul. With the STM-1 interface, the SAS-5000 can meet the demands of the highest capacity Node B sites. It also allows the re-provisioning of backhaul capacity, as Node B capacity increases, by changing the traffic descriptors on the traffic VCCs without having to visit the tower site and reconfigure the physical E1s. The STM-1 interface can also support interoperability with Node Bs from almost every mobile equipment vendor. The SAS-5000 will be housed in an 1-RU plastic enclosure that will be mounted on a 19 inch rack. Upon its initial release, the SAS-5000 will support 4 QAM operation for 28 MHz channels. 4000 Series Radio Units The new 4000 series radio units offer higher performance at a lower price than previous generation radio units, and support ETSI 26 GHz and ETSI 28 GHz frequency plans. The 4000 series Subscriber Radio Units (SRUs) support a 280 mm or 600 mm antenna option for maximum range, shown in Figure 3.3. The 4000 series Base Radio Units (BRUs), shown in Figure 3.4, support high-gain sectoral antenna options for maximum coverage with cosecant-squared shaping in elevation to eliminate the possibility of coverage drop-outs, close-in to the base station. Both horizontal and vertical polarization options are supported to maximize frequency reuse. The sectorization schemes include 180° and 90° options; and in the future, 45° and 22.5° for scalable capacity. Both the BRUs and SRUs provide 448 MHz of tuning bandwidth, minimizing the number of radio models that need to be stocked and spared.


airstar Access Network Components (cont’d) 4000 Series Radio Units Figure 3.3 SRU with 280 mm Antenna Option

Figure 3.4 BRU with High-Gain Antenna Option


airstar Access Network Components (cont’d) Base Station Integrated Shelf (BSIS) The BSIS shelf provides a complete four-sector, fully redundant base station with STM-1 capacity in a single chassis. It provides a total of 16 slots that can house two pairs of Base Station Modules (BSMs), each occupying two slots in the chassis, and four pairs of Base Modem Modules (BMMs). The BSMs provide the CellMAC control and ATM aggregation functionality. The BMMs provide the modem functionality for each base station radio. Front-Access Option For mobile transmission applications where the PMP base station resides in a tower shelter, space is limited; therefore, front-access to all field replaceable units is required. For these applications, a front-access BSIS option is available, shown in Figure 3.5. The dimensions for the BSIS front access option is 14-RU in height and 450 mm in depth, including the fan tray, plenum, and the cable management tray. Figure 3.5 Front-Access BSIS Shelf Configuration


airstar Access Network Components (cont’d) Redundancy airstar has always provided carrier-class redundancy at the base station, and the BSIS has extended the airstar industry leading, redundancy support. The redundancy switching time for the BSIS is typically six seconds, which is important for mobile transmission network applications. Especially, since some GSM BTSs can go into a reboot cycle after ten seconds of outage on their trunk, resulting in downtimes that can last minutes. Redundancy switching for the BMMs and BRUs is independent of the BSMs; therefore, an outage in one sector does not cause a redundancy switchover for the common equipment that would result in an outage in all the other sectors. CellMAC Air Interface The CellMAC is an SR Telecom patented ATM/TDMA (Time Division Multiple Access) air interface. It supports a Frequency Division Duplexing (FDD) architecture to maximize full-duplex capacity, which is essential for mobile subscriber traffic. A FDD scheme allows an airstar access network to conform to major standard frequency allocations worldwide. The air interface is Time Division Multiplexing (TDM) on an ATM cell-by-cell basis. The payload of each Media Access Control (MAC) packet is the payload of a single ATM cell. All subscriber services are adapted to ATM within the CPE. The CellMAC provides industry-leading quality of service (QoS) to support the following:

Constant bit rate (CBR) services provided for E1 and FE1 services

Subscriber traffic for 3G networks that can be mapped to a real time VBR (rt-VBR) traffic class

Data services that can be mapped to a non-real-time variable bit rate (nrt-VBR) traffic class, and both VBR.1 and VBR.3 modes are supported

Traffic scheduling is a main factor in achieving QoS delivery. The CellMAC controller Application Specific Integrated Circuits (ASICs) in the base station perform hardware-based scheduling algorithms using ATM Forum standard dual-leaky bucket algorithms.

For CBR traffic, this permits the assignment of arbitrary peak cell rates while minimizing cell delay variation, and accordingly overall end-to-end delay

For nrt-VBR traffic, this permit the delivery of arbitrary peak information rate (PIR) and committed information rate (CIR) traffic contracts

For rt-VBR traffic, a delay guarantee of the inverse of the peak cell rate is added.


airstar Access Network Components (cont’d) CellMAC Air Interface With nrt-VBR.1, subscriber traffic is strictly shaped to its peak cell rate (PCR), sustained cell rate (SCR), and maximum burst size (MBS) traffic contract, ensuring that the subscriber receives the precise service they have paid for. This preserves a service provider’s flexibility to persuade a subscriber to purchase a higher grade of service. With VBR.3, the subscriber is able to continue to burst at up to a PCR for bursts sizes larger than MBS that better maps to the manner in which Frame Relay services are delivered today. For bursts longer than MBS, the subscriber traffic is non-conforming to its traffic contract and is tagged with a CLP (cell loss priority) = 1 on a packet-contiguous basis so that it may be discarded if congestion is encountered further upstream in the ATM network. AirView Link Navigator Network Management System AirView Link Navigator is a carrier-class network management system (NMS) capable of managing a nationwide airstar network from a single network operations centre (NOC), shown in Figure 3.6. Link Navigator is built on a Java-CORBA client/server architecture supporting a many-to-many relationship between the graphical user interface (GUI) clients and the management servers. Using CORBA, the management servers can be distributed logically hardware hosts or distributed geographically to concentrate the management traffic at a regional level. Both the GUI clients and the management servers are 100% Java applications and can run on both Solaris and Windows® 2000 operating systems. Link Navigator provides complete fault, configuration, accounting, performance, and security (FCAPS) management functions for the airstar equipment. The southbound interface, from Link Navigator to the embedded airstar elements, is SNMP. The northbound interfaces for end-to-end provisioning and fault management applications are based on CORBA. The use of the CORBA northbound interfaces allow Link Navigator to abstract higher layer management applications from changes in the southbound SNMP interface, as the configuration of the embedded equipment changes from release to release. This method for northbound interfacing greatly facilitates the creation of an end-to-end NMS for multi-vendor ATM networks.


airstar Access Network Components (cont’d) AirView Link Navigator Network Management System Figure 3.6 AirView Link Navigator Main Screen


airstar Access Network Components (cont’d) Fault Management Link Navigator and the embedded SNMP agents use event-driven traps to communicate alarm information. This significantly reduces the rate required for polling each network element for its status; as a result, increasing the scalability of the management system. The trap mechanism is reliable and lost traps are collected on each polling cycle. Alarm information is transmitted upwards through the network hierarchy in the GUI display. An alarm list is provided in the bottom pane of the Link Navigator GUI. Link Navigator allows an operator to easily navigate to an affected network element by selecting the alarm in the alarm list.

Link Navigator can forward SNMP traps to third party fault management systems.

Configuration Link Navigator provides a hierarchical or tree view of the network topology, from a regional grouping down to each individual CPE. All configurations for an airstar SAS are performed through Link Navigator before a SAS goes into service. The service technician is not required to perform any manual configurations through a command line type craft interface. All services are provisioned in the "native language" of the service and automatically mapped to the ATM service classes and traffic descriptors. For example, Frame Relay services are provisioned in terms of PIR and CIR, and Link Navigator automatically translates this into PCR and SCR traffic descriptors. The user is abstracted from managing individual Virtual Path Identifiers (VPIs) and Virtual Channel Identifiers (VCIs) across the air interface. Link Navigator can support flow through provisioning from a service activation system through its northbound CORBA interface. Accounting An inventory of all network elements is available through Link Navigator. The parameters, such as the model number, the hardware revision, the software version, and the provisioned services of each network element is tracked and stored in the network topology database. Link Navigator allows a user to query the database based on the stored parameters to perform selective downloads of software patches or to identify network elements that require vendor recommended maintenance.


airstar Access Network Components (cont’d) Performance Monitoring Link Navigator routinely collects performance statistics at regular intervals, typically five minutes, and stores them in the central database. The airstar system supports G.826 performance statistics on the airlink, as well as performance statistics for each service. The performance statistics are available to any third party application using Structured Query Language (SQL) or Open DataBase Connectivity (ODBC) interfaces. Security Management Subscriber terminal authentication is provided through the use of the factory-configured IEEE MAC address for each SAS. Only subscriber terminals whose IEEE MAC addresses have been provisioned at the base station will be allowed to admit into the network. When a subscriber terminal with an unrecognized IEEE MAC address attempts admission into a base station, it will be rejected and an alarm will be sent to the element management system.

Corporate Headquarters 8150 Trans-Canada Hwy.

Montreal, QC H4S 1M5

Canada [email protected] www.srtelecom.com

Date post:	30-Sep-2014
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Airstar for Mobile Transmission Networks

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