The GSM networkA GSM network is a complex system composed by several components. The last mile of thissystem is the BTS (Base Transceiver Station). The BTS is responsible to transmit and receivethe RF (Radio Frequency) signals to the user terminal (cell phone, PDA, modem, etc). The BTSsare controlled by a BSC (Base Station Controller) that is connected to the MSC/VLR (MobileSwitching Center/Visitor Location Register). Basically, the MSC/VLR is responsible toauthenticate the user against the database (HLR - Home Location Register, AuC -Authentication Center).

The OpenBTS projectThe OpenBTS (Base Transceiver Station) project is an effort to construct an open-source Unixapplication that uses the Universal Software Radio Peripheral (USRP) to present a GSM airinterface ("Um") to standard GSM handsets and uses the Asterisk software PBX to connectcalls.The OpenBTS uses the USRP hardware to receive and transmit the GSM signaling. This is doneby using the GNU Radio framework. The Asterisk is used to interface the GSM calls betweenthe cellular phones under the OpenBTS network. Any other device that can be connected tothe Asterisk can be also used

The OpenBTS uses the USRP hardware to receive and transmit the GSM signaling. This is doneby using the GNU Radio framework. The Asterisk is used to interface the GSM calls betweenthe cellular phones under the OpenBTS

Safety InformationCautionNortel Networks products are designed to work with single-phase power systems having agrounded neutral conductor. To reduce the risk of electric shock, do not plug Nortel Networks products intoany other type of power system. Contact your facilities manager or a qualified electrician if you are notsure what type of power is supplied to your building.CautionNot all power cords have the same ratings. Household extension cords do not have overloadprotection and are not meant for use with computer systems. Do not use household extension cords withyour Nortel Networks product.CautionYour Nortel Networks product is shipped with a grounding type (three-wire) power cord. Toreduce the risk of electric shock, always plug the cord into a grounded power outlet.Lithium Battery CautionsCautionThis product contains a lithium battery. Batteries are not customer replaceable parts. They mayexplode if mishandled. Do not dispose of the battery in fire. Do not disassemble or recharge.(Norge) ADVARSELLitiumbatteri - Eksplosjonsfare. Ved utskifting benyttes kun batteri som anbefaltav apparatfabrikanten. Brukt batteri returneres apparatleverandren.(Sverige) VARNINGExplosionsfara vid felaktigt batteribyte. Anvnd samma batterityp eller enekvivalent typ som rekommenderas av apparattillverkaren. Kassera anvnt batteri enligt fabrikantensinstruktion.(Danmark) ADVARSEL! Litiumbatteri - Eksplosionsfare ved fejlagtig hndtering. Udskiftning m kunske med batteri af samme fabrikat og type. Levr det brugte batteri tilbage til leverandren.(Suomi) VAROITUSParisto voi rjht, jos se on virheellisesti asennettu. Vaihda paristo ainoastaanlaitevalmistajan suosittelemaan tyyppiin. Hvit kytetty paristo valmistajan ohjeiden mukaisesti.

Despite the large number of authors, co-authors and editors, we have done our best to make the style of the book similar in all chapters and highly comprehensible. The content is presented in a well-structured manner; it is broken up into many titles and subtitles, which make its reception easy and looking up information in the text quick. The present book is written by programmers for programmers. The authors are active software developers, colleagues with genuine experience in both software development and training future programmers. Due to this, the quality of the content presentation is at a very good level, as you will see for yourself. All authors are distinctly aware that the sample source code is one of the most important things in a book on programming. Due to this very reason, the text is accompanied with many, many examples, illustrations and figures. When every chapter is written by a different author, there is no way to completely avoid differences in the style of speech and the quality of chapters. Some authors put a lot of work (for months) and a lot of efforts to make their chapters perfect. Others could not invest too much effort and that is why some chapters are not as good as the best ones. Last but not least, the experience of the authors varies some have been programming professionally for 2-3 years, while others for 15 years. This affects the quality, no doubt, but we assure you that every chapter has been reviewed and meets the quality standards of Svetlin Nakov and his team. C# and .NET Framework This book is about programming. It is intended to teach you to think as a programmer, to write code, to think in data strucSecured Unified Networks IP Stimulus (UNIStim) signal encryption isprovided by Datagram Transport Layer Security (DTLS), which encryptsthe data exchanges between the Signaling Server and the IP Phones.Previously, Secure Multimedia Controllers (SMC 2450) were required forUNIStim encryption, but DTLS requires no new additional hardware andcan coexist with currently installed SMCs. DTLS and non-DTLS systemscan be configured on the same network.To enable DTLS encryption, the Communication Server (CS) 1000 systemmust be upgraded to CS 1000 Release 6.0 and the IP Phones must havethe latest firmware. Also, the system has to be configured with at least theBasic Security level.Note: This feature does not provide signaling encryption for the UnifiedNetworks IP Stimulus File Transfer Protocol (UFTP), which is usedwhen transferring firmware to IP Phones. Firmware data contains nosensitive information and is protected from third-party tampering by adigital signature. Notifications from the signaling server to the phonesare sent using DTLS-protected UNIStim signaling to protect the signalsfrom intercept.DTLS and IP Phone registrationThere are two modes of IP Phone registration: Secure Handshake modethe IP phone is configured to initiate aDTLS session immediately upon beginning registration. Switchover modethe IP phone is configured to first establish anunencrypted Reliable User Datagram Protocol (RUDP) session tothe Line Terminal Proxy Server (LTPS),