CODEWITHSUNDEEP
cellular-networklteloralorawan
DevDevDev
DevDevDev

Reputation: 5177

Using consumer cellphones to build a mesh network for IOT devices?

I have been looking into LoRaWAN for a low cost waterproof asset tracker I am looking at building. AFAIK, the primary benefits of LoraWAN over say LTE-M or cellular are: no connectivity costs and potentially lower power consumption.

What I'm wondering is: why can't we use our own cellphones as the "base station" that the IOT device talks with? We can do this with bluetooth and WiFi, why not cell? Is it the LTE protocol that prevents it? Physics? What am I missing?

Upvotes: 1

Views: 124

Answers (2)

Karthik Balaguru
Karthik Balaguru

Reputation: 7852

The LTE relay interface inducted as part of Release 10 allows the deployment of relay nodes (a kind of low cost eNB) that are fixed and that use in-band LTE to extend the coverage of standard eNodeBs by one hop, improve signal quality and to increase the network capacity. Relays can be placed such that it converts the long single hop into two shorter hops.

However the approach of using UE seems have many challenges as it can make UE to get bit loaded with more functional changes across layers(MAC, PHY, RRC, NAS) as it has to take additional functionalities from Relay nodes/eNB as well ranging from lower layer signalling, co-ordination, mobility to forwarding. Also, there might be additional power consumption and change in antenna to support the same which all will add to more cost of UE.

Upvotes: 0

Nick
Nick

Reputation: 535

There's quite a few architectural reasons why Peer-to-Peer LTE isn't feasible, but the largest is probably the fact that in LTE the uplink and downlink use different modulation techniques.

In the downlink (the connection from the Base stations (eNodeBs) to the User Equipment (our mobile phones)) Orthogonal Frequency Division Multiplex (OFDMA) is used, this means the phone listens out onto the RF interface for the OFDMA signal.

This works well, OFDMA is a great way of encoding the data onto the air interface, but it has a very high peak-to-average-power ratio, this means if the UEs used OFDMA in the Uplink (From the UE to the eNodeB) they'd have awful battery life.

Instead in the Uplink LTE uses Single Carrier Frequency Division Multiple Access (SC-FDMA), which is much more power efficient and allows you talk all day, so the eNodeBs listen on their RF interface for the SC-FDMA modulated traffic.

This means our UEs (Mobile phones) use one type of modulation to send and a different modulation scheme to receive, so they can't talk directly to one another as they can't send OFDMA modulated data, only receive & visa-versa.

Some more reading on OFDMA & SC-FDMA.

Upvotes: 0

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