Conceivable range for peer to peer messaging?

[DaraParsavand]

I'm very interested in the ability of Android phones to send a text
message from one phone to another without using a cell tower (peer to
peer). I haven't yet found something online that discusses the
particular physical channel used for this purpose - I hope it isn't
limited to something like bluetooth. What is the maximum conceivable
range given US FCC laws of the peer to peer message? Could it be
longer in other countries? In this group, I searched for the word
peer and I looked over the API top-level documentation. Is anything
known yet?

In particular, I've always wanted an alternative to shouting climbing
commands to my partner and FRS radios have always seemed unappealing,
big, heavy, and noisy. I'd much rather text message ability and
heck, I'd have my phone with me anyway which may have coverage on
parts of the climb. This is a 60 m range problem and sometimes around
the corner of a rock rib (which could require some significant Eb/No
at the output device, but then that is one of the points of messaging,
keep the #of bits low and low power can still work great).

Dara Parsavand

[Mac Chew]

Bluetooth,
Ref: http://en.wikipedia.org/wiki/Bluetooth
Transmission range depends on which Class the device is.

For most Mobile phone/pda, the Bluetooth Class is Class 2, with a
transmission range of 10 meters.

On Dec 21, 2:34 pm, DaraParsavand <dara.parsav...@gmail.com> wrote:
> I'm very interested in the ability of Android phones to send a text
> message from one phone to another without using a cell tower (peer to
> peer). I haven't yet found something online that discusses the
> particular physical channel used for this purpose - I hope it isn't

> limited to something likebluetooth. What is the maximum conceivable

[DaraParsavand]

On Dec 25, 5:26 pm, Mac Chew <mac.c...@gmail.com> wrote:
> Bluetooth,
> Ref:http://en.wikipedia.org/wiki/Bluetooth
> Transmission range depends on which Class the device is.
>
> For most Mobile phone/pda, the Bluetooth Class is Class 2, with a
> transmission range of 10 meters.

Thanks, I hadn't read that wiki article before and didn't know there
was a class 1, 20 dBm, 100 m option. That might be sufficient for
what I want, though I'm afraid the frequency of Bluetooth doesn't
propagate well on rock climbs that aren't line of sight (one fellow
engineer suggested looking into the CB band and see what kind of low
rate digital information can be put on that band - I think he said
some transceivers can send several tone pairs, so it would be
conceivable to send really low rate digital messages this way).

The Bluetooth article says 20 dBm output at let's say 1 Mbps (1 and 3
Mbps rates are mentioned) can go 100 m. Ignoring the complexities of
demod tracking loops and such, if I'm willing to transmit information
much more slowly, I can reduce the output power proportionately. I
don't need 1Mbps, I need more like 1kbps (after all, my text messages
would be a few kb at most usually). That means -10 dBm output power
which is lower than even a class 0 device. I'd rather output at
class2 (4 dBm) and have lots of data rate options to get as far as
possible (several km would be nice - I'd like to match the range of
voice transmission of FRS radios).

Is it the case that this peer to peer Android function will only use
Bluetooth? Is anyone talking about any other protocols? WiFi,
Zigbee, or a bunch of other options I've probably never heard of?

(and is this the right forum to discuss this?)

Thanks,
Dara Parsavand

[Victo...@gmail.com]

It will probably be easier to use WiFi netork for this application.
Most WiFi devices support ad-hoc mode so you can make 2 phones talk to
each other (Sony PSP uese this capability to allow you to play game
with your friend).

Once you establish WiFi link between 2 phones and assign IP addresses,
you can build peer-to-peer applicaitons to have 2 phones talk to each
other.

Most WiFi devices in current phones support 15-20dbm and you should be
able to get 50-100m, depends on environement.


Victor