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Manajemen Lokasi

Manajemen Lokasi. Handover. process of changing the channel (frequency, time slot, spreading code, or combination of them) associated with the current connection while a call is in progress Handoff is divided into two broad categories: hard handoffs soft handoffs

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Manajemen Lokasi

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  1. Manajemen Lokasi

  2. Handover • process of changing the channel (frequency, time slot, spreading code, or combination of them) associated with the current connection while a call is in progress • Handoff is divided into two broad categories: • hard handoffs • soft handoffs • They are also characterized by “break before make” and “make before break.”

  3. Types of Handover • hard handoffs. • soft handoffs.

  4. hard handoffs • hard handoff can be further divided into two different types : • Intra handoffs • intercell handoffs

  5. hard handoffs

  6. hard handoffs • A hard handoff is essentially a “break before make” connection. • Under the control of the MSC, the BS hands off the MS’s call to another cell and then drops the call. • In a hard handoff, the link to the prior BS is terminated before or as the user is transferred to the new cell’s BS; the MS is linked to no more than one BS at any given time.

  7. hard handoffs • Hard handoff is primarily used in FDMA (frequency division multiple access) and TDMA (time division multiple access), where different frequency ranges are used in adjacent channels in order to minimize channel interference. • So when the MS moves from one BS to another BS, it becomes impossible for it to communicate with both BSs (since different frequencies are used).

  8. hard handoffs • A hard handoff occurs when the old connection is broken before a new connection is activated

  9. hard handoffs • a MS moving from one BS (BS1) to another (BS2). • The mean signal strength of BS1 decreases as the MS moves away from it. • Similarly, the mean signal strength of BS2 increases as the MS approaches it. • This figure is used to explain various approaches described in the following subsection.

  10. hard handoffs

  11. HANDOFF DECISION • Network-Controlled Handoff • Mobile-Assisted Handoff • Mobile-Controlled Handoff

  12. Network-Controlled Handoff • the network makes a handoff decision based on the measurements of the MSs at a number of BSs. • In general, the handoff process (including data transmission, channel switching, and network switching) takes 100–200 ms. • Information about the signal quality for all users is available at a single point in the network that facilitates appropriate resource allocation. • Network-controlled handoff is used in first-generation analog systems such as AMPS (advanced mobile phone system), TACS (total access communication system), and NMT (advanced mobile phone system).

  13. Mobile-Assisted Handoff • In a mobile-assisted handoff process, the MS makes measurements and the network makes the decision. • In the circuit-switched GSM (global system mobile), the BS controller (BSC) is in charge of the radio interface management. • This mainly means allocation and release of radio channels and handoff management. • The handoff time between handoff decision and execution in such a circuit-switched GSM is approximately 1 second.

  14. Mobile-Controlled Handoff • In mobile-controlled handoff, each MS is completely in control of the handoff process. • This type of handoff has a short reaction time (on the order of 0.1 second). • MS measures the signal strengths from surrounding BSs and interference levels on all channels. • A handoff can be initiated if the signal strength of the serving BS is lower than that of another BS by a certain threshold.

  15. Soft handoff • The soft handoff can also be divided into two different types : • multiway soft handoffs • softer handoffs

  16. Soft handoff • In this case the connection to the target is established before the connection to the source is broken, (make-before-break). • The interval, during which the two connections are used in parallel, may be brief or substantial. • For this reason the soft handover is perceived by network engineers as a state of the call, rather than a brief event.

  17. Soft handoff • Soft handovers may involve using connections to more than two cells: connections to three, four or more cells can be maintained by one phone at the same time. • When a call is in a state of soft handover, the signal of the best of all used channels can be used for the call at a given moment or all the signals can be combined to produce a clearer copy of the signal.

  18. Soft handoff • The latter is more advantageous, and when such combining is performed both in the downlink (forward link) and the uplink (reverse link) the handover is termed as softer. • Softer handovers are possible when the cells involved in the handovers have a single cell site.

  19. Soft handoff

  20. Faktor Kegagalan Handover • Peningkatan jumlah panggilan (call_attemp) • Jumlah panggilan (call_attemp) yang berlangsung dalam sistem komunikasi selular dapat mempengaruhi tingkat kegagalan yang terjadi pada handover.

  21. Faktor Kegagalan Handover • Interferensi • Gangguan yang disebabkan karena adanya sinyal lain yang tidak dikehendaki yang frekuensinya sama atau hampir sama dan dayanya cukup besar yang masuk bersama dengan sinyal yang seharusnya diterima. • Dalam sistem komunikasi selular dapat dimungkinkan terjadi penggunaan frekuensi yang sama pada dua atau lebih kanal.

  22. Faktor Kegagalan Handover • Propagasi • Propagasi adalah pelemahan yang diperkirakan akan dialami sinyal dari Base Station (BS) ke mobile station (MS). • Hal ini disebabkan adanya pergerakan dari MS yang menyebabkan kuat sinyal yang diterima MS bervariasi

  23. Faktor Kegagalan Handover • Fading • Perubahan kuat sinyal yang terjadi akibat gangguan propagasi, seperti adanya pemantulan yang disebabkan oleh kontur alam, gedung, rumah dan lain-lain.

  24. References • http://media.johnwiley.com.au/product_data/excerpt/28/04714190/0471419028.pdf • http://en.wikipedia.org/wiki/Handover#Types_of_handover • http://www.elektro.undip.ac.id/el_kpta/wp-content/uploads/2012/05/L2F007036_MKP.pdf

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