MRF24J40-ISLASHML datasheet(97/151 Pages) MICROCHIP

97 / 151 page

 2021 Microchip Technology Inc.

Preliminary

DS30009776E-page 97

MRF24J40

3.7

Link Quality Indication (LQI)

Link Quality Indication (LQI) is a characterization of

strength or quality of a received packet. Several

metrics, for example, RSSI, Signal to Noise Ratio

(SNR), RSSI combined with SNR, etc., can be used for

measuring link quality. Using RSSI or SNR alone may

not be the best way to estimate the quality of a link. The

received RSSI value will be a very high value if a packet

is received with greater signal strength or even if an

interferer is present in the channel. Hence, for better

approximation of link quality, the MRF24J40 reports the

correlation degree between spreading sequences and

the incoming chips during the reception of a packet.

This correlation value must be directly mapped to a

range of 0-255 (256 values) using software, where an

LQI value of 0 indicates that the quality of the link is

very low, and an LQI value of 255 indicates the quality

of the link is very high. The correlation degree between

spreading sequences and incoming chips is computed

over a period of 3 symbol periods during the reception

of the preamble of a packet.

EQUATION 3-1:

LQI

LQI (0-255) = (CORR - a).b

where,

• CORR = LQI reported along with each packet in

the RX FIFO, as shown in Figure 3-2.

• a = 50

•b = 4

- Values of ‘a’ and ‘b’ are found empirically

based on Packet Error Rate (PER) measure-

ments as a function of the correlation value.

3.8

Beacon-Enabled and

Nonbeacon-Enabled Networks

The IEEE 802.15.4 Standard defines two modes of

operation:

• Beacon-enabled network

• Nonbeacon-enabled network

3.8.1

BEACON-ENABLED NETWORK

In a beacon-enabled network, beacons will be transmit-

ted periodically by the PAN coordinator. These

beacons are mainly used to provide synchronization

services between all the devices in the PAN and also to

support other extended features, like Guaranteed Time

Slots (GTS), a Quality of Service (QoS) mechanism for

the IEEE 802.15.4 Standard. The PAN coordinator

defines the structure of the superframe using beacons.

MRF24J40-I/ML Datasheet(PDF) 97 Page - Microchip Technology

MRF24J40-I/ML Datasheet(HTML) 97 Page - Microchip Technology

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 ...More

Datasheet Download

Link URL