What is Evolution Data Optimized (EVDO)?

 What is Evolution Data Optimized (EVDO)?

What is Evolution Data Optimized (EVDO)?

Evolution Data Optimized (EVDO) is a high rate packet data. It was implemented to optimize forward link throughput, but several subsequent releases have focused on improvement not only on the forward link but also to the reverse-link throughput. EVDO was initially a single carrier.

1xEV-DO is a packet data-only system. Hence, it has many advantages for handling data in both stationary and non-stationary environments.

EVDO is a single carrier occupying 1.25 MHz spectrum in an FDD configuration. It uses a chip rate of 1.288 Mcps which is the same as 1xRTT.

1xEVDO is deployed as an overlay system in conjunction with 1xRTT network. It uses the same attributes as 1xRTT. The interaction between 1xEV-DO and 1xRTT systems is achieved through initial system acquisition and when the data session it is possible to hand off from 1xEVDO to 1xRTT system migrating from EVDO to a 1xRTT network.

However, there are fundamental differences between EVDO and 1xRTT in that in an EVDO network, transmission occurs only on the best link possible i.e. there are no soft and softer handoffs. This process is called as virtual soft handoff.

For obtaining a soft handoff, the mobile unit observes the Signal to Interference and Noise Ratio (SINR) of the pilots in the active set and informs the network through the reverse channel of the identity of the best serving cell.

On the forward link rate adaption is used.

With EVDO, the mobile terminal plays a predominant role in transmission rate selection involving closed-loop rate control. In closed-loop rate control, the terminal predicts the channel condition using a predicted SINR that is based on current packets received. When the network accesses a terminal, it selects the most recent rate fed back from the terminal itself.

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