10. Dss «Kvant-e». Subscriber access subsystem. Analogue subscriber lines including.

Subscriber access subsystem includes three subsystems listed below.

Narrowband subscriber access subsystem provides Z interfaces for analogue subscriber lines and U or S interfaces for digital subscriber lines. This subsystem provides an appropriate signaling for the last mile and multiplexes subscriber traffic. It uses Dual-Tone Multi-Frequency signaling for analogue subscriber lines and EDSS1 (European Digital Subscriber Signaling) signaling for digital subscriber lines. Physically this system is implemented in analogue customer units, network terminations, line terminations and terminations of ISDN BRA (2B+D) lines.

Broadband subscriber access subsystem provides interfaces for digital subscriber lines of high bit rates (like SDSL or ADSL lines). This subsystem supports xDSL liens, symmetric lines (with the V5.2 interfaces) towards OLTs (Optical Line Termination) of PON subscriber access network, SDH and Ethernet lines. ATM/Ethernet switch enables implementing of this subsystem.

Wireless subscriber access subsystem provides access for fixed and mobile subscribers. This subsystem includes base stations controllers (BSC), base stations (BS), base stations multiplexers (BSM), fixed terminals, and portable terminals. The base stations controller controls the DECT wireless access network. The base stations provide radio channels for terminals. The base stations multiplexer multiplexes/demultiplexes E1 trunks (running from the BSC) and controls several base stations. The portable terminal provides wireless access (to a base station) for mobile (within 300-600 meters) subscribers. Fixed terminals gain access to the network with the help of Fixed Access Units (FAU). The Fixed Access Unit can operate 1.5-10 kilometers away from a base station. The fixed terminals are connected to the FAU directly via usual wire subscriber lines.

Network access subsystem provides interfaces for trunks towards other TEs or nodes of a telephone network. Thus, it coordinates internal trunks with external ones. Digital trunk units (DTU) represent this subsystem. For example interfaces A or A₁ for digital trunks, interfaces C₂ for 2 or 3-wire physical trunks, C₁ interfaces for TDM trunks.

Signaling subsystem provides exchange of line and control signals (including subscriber signaling) in internal and external connection directions. It supports the following types of signaling:

1. Subscriber signaling (connection request, dialing, answer, “on-hook”);

2. Inner signaling and signaling towards other TEs. For example, it provides MFC towards ATSK-U. MFC conveys line signals over 16-th TS and control signals over voice channels.

3. SS7 signaling towards other digital TEs can handle up to 2000 information channels.

Synchronization subsystem provides cycle and multi-frame synchronization for digital flows.

Power supply subsystem provides primary power supply (±60V or ±48V) and secondary power supply (±5V, ±12V, and so on).

Control subsystem controls the whole switching system. It includes a central controller and controllers of every module of the switching module.

Maintenance and operation subsystem allows to perform system diagnostic and maintenance functions. An operator can test modules, measure electric parameters, measure traffic parameters. Physically, the subsystem can be implemented in the maintenance workstation that can interact with Telecommunication Management Network.

A digital witching system can use some facilities to provide additional services.

Internet Point of Presence provides dial-up subscriber access to Internet. IPOP includes multifunctional Internet servers. These servers require definite throughput of a switching network. This means that IPOP requires serial customer units for a modem pool.

Service Switching Point (SSP) provides Intelligent Network services. SSP is usually housed with TX. SSP allows to split switching and services (and spread logic of services all over the net). This allows to create new services fast. SSP enable such services as free phone, Account Calling Card, Televoting and others.

Main units (like switching units, control units, power supply units) of a digital switching system are backed up in order to increase reliability.

The table below shows some parameters of the most common digital switching systems.

Characteristic	EWSD V15	5ESS	SI2000 V5	Kvant-E	ES-11	Dnipro
Application	TX, HTE, HE, MSC, SSP, Call-center	TX, HTE, MSC, SSP, Call-center	HTE, HE, CE, NE, TE, Call-center	HTE, HE, CE, NE, TE	HE, CE, NE, TE,	HTE, HE, PE, CE, NE, TE
Maximum capacity	over 500 000	over 500 000	100 000	100 000	13500	up to 30 000
RSwMs, RSubMs capacities	1984, 3986 for RDLU; up to 50 000 for RSU	up to 3552 for RAIU; 12000 for MMRSM; 25000 for VCDX	miniAN-320; AN-704; SAN-2800	SLU-128, 256	SM-150, 240, 480	62, 496, 992, 1488, 1984
Broadband access	IPOP/ PHUB DLU-IP SURPASS	BAIU	BAN mBAN μBAN IP BAN	–	–	–
Additional services	100	100	30	25	15	20
Optical interfaces	STM-1	STM-1	STM-1	–	–	PDH: E1 E2 E3