Developing Mobile Applications

Transcription

1 Developing Mobile Applications 3G and IMS 1

2 3G two things The most important aspect of 3g is the new frequency space. up to 155MHz of new bandwidth one carrier is 5MHz wide A general purpose network infrastructure and a end-to-end (operator controlled) approach when developing new services. 2

3 Code Division Terminals send on the same frequency but use different codes. Codes are used to separate signals not for encryption nor authentication. Base stations close to each other must use different codes similar to GSM networks where base stations must use different frequencies. Cell planning is not trivial! 3

4 bit rates 2G + GPRS 171 kb/s 3G first round EDGE 384 kb/s WCDMA 2 mb/s 3G today HSDPA >10 mb/s 4

5 shared bit rates Comparing the shared capacity of one carrier is like comparing MHz figures of computer or the speedometer of sports cars. how much bandwidth is available what is the expected throughput for a user 5

6 triple the bit rate 4s at 40Kbps 10 K byte 2.5s at 120Kbps 10 K 6

7 A question... Is HSDPA a WLAN hot-spot killer? Is it a ADSL killer? 7

8 the difference downloading of media files streaming video killer app for 3G support for more users voice at very low cost 8

9 What service GGSN/APN 9

10 IP to the terminal Mobile networks in past: Voice used dedicated infrastructure IP was riding on voice Mobile networks now Voice uses dedicated infrastructure IP uses dedicated infrastructure Mobile networks tomorrow IP uses dedicated infrastructure All services on top of IP 10

11 How much... Willingness to pay charge Needed bit rate 11

12 What if we differentiate the cost? Willingness to pay charge Needed bit rate 12

13 Two solutions Differentiate depending QoS: time of day bit rate reliability Differentiate depending on service mp3 song or a short message voice or radio streaming How do ISP do? 13

14 service description A terminal will negotiate a service level agreement when accessing a service. The agreement is based on the subscription needed service network load 14

15 QoS classes conversational symmetric, low delay, constant bit rate streaming asymmetric, higher delay, constant bit rate interactive web surfing, chat,... back ground , synchronization,... 15

16 service attributes maximum bit rate guaranteed bit rate delivery order (no for IP) bit error rates transfer delay 16

17 QoS business models different QoS agreements open up for different charging mechanism: high cost real time point-to-point video low voice calls, surfing, ,... dirt cheap synchronization at 3 o'clock in the morning 17

18 What if QoS is not enough? IMS 18

19 IP Multimedia Subsystem HSS SIP-proxy SIP SIP-server any network application servers 19

20 The nodes HSS home subscriber server similar to the HLR user data location S-CSCF server allocated CSCF - call session control function a SIP server Proxy, serving and interrogating 20

21 A terminal... Attaches to IMS when... turned on. Connects to an allocated P-CSCF and is authenticated. The P-CSCF will through out the session work on behalf of the terminal. Other nodes will trust the P-CSCF. P-CSCF will compress SIP traffic directed to the terminal. 21

22 The SIP server A terminal registers with a S-CSCF. The S-CSCF now holds the IP address connected to the SIP-address. The HSS is updated so we know which S-CSCF to contact. S-CSCF is protected from outside access by I-CSCF (Interrogating) I-CSCF are SIP routers that connect IMS systems of different mobile networks. 22

23 Applications SIP-proxy SIP-server SIP application servers 23

24 IMS applications IMS applications Native, on SIP application servers Through gateways to existing GSM services PSTN applications can be connected over a BGCF (Breakout Gateway) First IMS applications messaging voice mail conference call 24

25 the real 3G challenge Application environment Screen size Browser capabilities Runtime environment (Java,..) Variable bit rate 1Mb/s to 9 Kbps in 10 seconds! 25