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To: w molloy who wrote (18656)	11/20/1998 9:53:00 PM
From: freak.monster1	Read Replies (1) \| Respond to of 152472

>To get 144kbps, they are going to have to lump channels >together. I will be surprised if the network providers go >for it. GSM is >proposing the same with multi-timeslots. I believe you are thinking of IS-95B MDR. In IS-95B, higher data rates are achieved through concatenating multiple channels. 1XRTT has an entirely new forward and reverse link modulation (and other changes) and increased data rate is not achieved through concatenation.Also, 1XRTT has much improved provisioning for packet switched data which enables the capacity to be shared much more effeciently among users. That is not to say of course (as has been commented on in another thread) that there is not a finite capacity per sector. Only that capacity has doubled with IXRTT as compared to IS-95A/B air interface. This is NOT the same thing as GSM. In GSM you start assigning more slots to one user (which incidently makes for a full-duplex mobile receiver, thus adding complexity to the mobile compared with voice only GSM mobile. CDMA voice only mobile is full-duplex to start with). >The writer appears to be contradictory when he suggests a data >rate of 300kbps from a 144kbps packet data service. I don't think that is being said, nor is it contradictory. IXRTT allows for peak data rates to a particular user of upto 300kbps (depending on channel condition, cell loading, position of the user in the cell etc). >I suspect >that they will specify what is called an unbalanced link, where >the data rate in one direction is much less than the data >rate in the other direction. He may also be referring to some >other unspecified (connection oriented?) service. 1XRTT doesn't specify whether the link is balanced on not, but I agree that in practice most user require more data than they originate (web browsing for example). I believe the peak data rate supported in Forward Link is double the peak rate on the reverse link. Within these peak rates, a user can definitely have a symmetric link. >I don't know what the writer means by two fold increase in voice >capacity.... Does he mean channels? Yes. One 1.25MHz bandwidth will be able to sustain twice the number of voice calls compared with IS-95A. Without loss of quality. 1XRTT is twice as efficient in using the bandwidth. The bits/Hertz has doubled (on average for a sector). >Increased Voice capacity >generally comes with degraded voice quality. As I understand >that 8.5kbps voice is being quietly dropped in favour of 13.3kbps >voice,I don't know how this will be achieved. I'm no longer >working on CDMA so I guess I will never know... This is true if you assume that the capacity of your link has not changed. In the case of 1XRTT it has doubled. So the increase in the number of users is NOT at the expense of reduced voice quality. In fact the peak as well as the average voice data rates will remain the same as before (8K or 13K peak rate). Regards.