3G PARAMETERS

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3G PARAMETERS

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The calculation parameters for third generation mobile UMTS y CDMA2000 are:

params_3g_umts

Number of users. Average number of users per cell, regardless of whether they are or not in the handover.

Power Increasing (dB). In radio planning of cellular networks it is been used averaged magnitudes over fast multipath variations. Thus, the received signal power (sensitivity) and the attenuation of propagation (basic loss) are average values.

Similarly, the transmitted power is an average over the rapid changes imposed by the power control, which tries to compensate for multipath fading. In a classical system (without fast power control), the received power S can be obtained from the transmitted power Pt and the propagation basic losses Lb (average values over rapid variations) like:

S = Pt-Lb+Gt+Gr-L0 (1)

where Gt and Gr are the antennas gains, and L0 is a term of additional losses (cables, coupling elements, user's body).

In CDMA systems, the existence of a fast power control makes the expression (1) ceases to be valid. To satisfy equality in the expression it is necessary to subtract a term called transmit power rise, I, so:

S = Pt-I-Lb+Gt+Gr-L0 (2)

Physically, the term I means that it is required a higher average transmission power for the same average power at reception, compared to a system without fast power control. The extra power is not used for increasing the average power received, but for the power received to have less variation. This term usually take values between 0 and 3 dB, depending on propagation conditions (mainly on the speed of user movement).

Orthogonality factor. It is defined as the rate between the interference observed in a user's mobile of two orthogonal signals transmitted by the base station and the interference that would occur if said signals were pseudo-random. The orthogonality factor is independent of the spreading factor used, and varies between 0 (total orthogonality, corresponding to a channel without temporal dispersion) and 1 (total loss of orthogonality, in a highly dispersive channel)

Shadow fading margin. Shadow fading is the decrease in received power relative to its long-term average value. This shadow fading is a random variation produced by the presence of obstacles in the transmitter-receiver path not considered by the deterministic model. To prevent this fading from causing an interruption of the 3G service, an additional loss or additional margin is established that must be taken into account along with the rest of the losses. It is also known as the "log-normal" margin.

SHO gain by shadow fading. When evaluating the cell coverage can be assumed that users located on the cell's edge are in a position to handover continuously (soft handover) with one or more neighboring cells, so they are received simultaneously at several bases. As a result, there is improvement due to reception diversity. One effect of this diversity is that the margin necessary to take into account the shadow fading is less than the one that would exist with a single base. There is thus a gain term, which must be subtracted from the log-normal margin calculated as usual. If in this margin calculation has been taken into account this effect is not necessary to apply any corrections.

SHO multipath gain (dB). Another effect of the reception diversity associated with the handover is a decrease in the required EB/N0 ratio. As in the previous case, if the EB/N0 value specified already takes into account the gain per handover it is not necessary to apply any correction. Typical values are between 0 and 2 dB.

Bit rate DL. Required bit rate in the mobile terminal to provide a certain service.

Eb/N0 DL. Required Eb/N0 ratio in the downlink, referred to the source bit rate. Downstream, the physical data (DPDCH) and control (DPCCH) channels are time multiplexed, and the specified Eb/N0 must take into account the overhead introduced by the control channel.

Bit rate UL. Required bit rate that the mobile terminal has to transmit to provide a certain service.

Eb/N0 UL. Eb/N0 ratio required in the uplink, referred to the source bit rate.