Baud rate for p25 Bedford Police Dept.

[N_Jay]

Wow! If I just got that detail from the onset I would have not been confused. However, you did use confuse more than a few times in your detailed paragraphs (Ha, Ha, Ha).I agree as you have said: "If we would just clearly say what we really mean and get rid of the shorthand it would be so much easier." Bravo!

Would be nice if the shorthand was eliminated or minimized, but I have received considerable push-back when I have suggested such "foolish" ideas in the past. :roll:

 

[RKG]

Excellent info---very clear.

But of course a few other items come to mind now. So if a system is trunked p25 would that be considered the 9600 bps system? You said if "using P25 voice, that would narrow it down to two possibilities"

Motorola
P25 Standard

Is p25 standard and Motorola voice considered the 3600bps? Meaning dispatch is communicating via voice protocal?

What then is the focus on the P25 9600 BPS. Is that consider trunked p25---digitized voice?

Thank you in advance UPMAn.

Not quite:

1) "Baud rate" refers to the rate at which the control channel sends data. Necessarily, this relates only to trunked systems.

2) Motorola SmartNet/SmartZone systems are considered "3600 baud," because they send data at 3600 bps. Motorola "Astro 25" systems are considered "9600 baud" even though they send data at the rate of 4800 bps; the difference is that the "bit" sent by the "Astro 25 " system has four states and therefore can serve the function of two binary bits.

3) By itself, "P25" or "Project 25" or "APCO 25" or "CAI" refer to a particular (proprietary) means of encoding analog voice into a digital datastream, in this case using the IMBE vocoder produced by a company called DVSI. CAI voice can be sent over the air on a conventional channel, a SmartNet/SmartZone voice channel, or an "Astro 25" voice channel.

4) "Astro 25" is a Motorola proprietary term that refers to a particular type of trunked radio system. The terms "P25" (referring to a particular voice encoder method) and "Astro 25" (referring to a particular trunking control system) are not synonymous.

 

[N_Jay]

Not quite:

1) "Baud rate" refers to the rate at which the control channel sends data. Necessarily, this relates only to trunked systems.

Baud rate is the rate at which the system sends symbols, not necessarily the same as the data rate (the rate at which it send bits since a symbol may represent more than one bit)

2) Motorola SmartNet/SmartZone systems are considered "3600 baud," because they send data at 3600 bps. Motorola "Astro 25" systems are considered "9600 baud" even though they send data at the rate of 4800 bps; the difference is that the "bit" sent by the "Astro 25 " system has four states and therefore can serve the function of two binary bits.

Motorola (SmartNet-SmartZine, Privacy Plus, etc.) are "called" 3600 baud, because people like to.
They do send data on teh control channel at 3600 BPS in a 2 level FSK format so the baud rate is also 3600.
Motorlola "ASTRO25" is their brand name for their P25 systems, and like all P25 systems send data at a 9600 BPS rate using a 4 level FSK format, so the baud rate is actually 4800. (2 bits per symbol, or sometimes called a di-bit, but NEVER just a "bit")

3) By itself, "P25" or "Project 25" or "APCO 25" or "CAI" refer to a particular (proprietary) means of encoding analog voice into a digital datastream, in this case using the IMBE vocoder produced by a company called DVSI. CAI voice can be sent over the air on a conventional channel, a SmartNet/SmartZone voice channel, or an "Astro 25" voice channel.

By itself "P25" or "Project 25" or incorrectly, but historically called "APCO 25", or referred to as the "Common Air Interface" (CAI) (More correctly the P25 CAI, but why be accurate with short-hand) is a STANDARD, NON-PROPRIETARY set of standards that includes several specifications, one of which is "a particular means of encoding analog voice into a digital datastream, using IMBE". Additionally it contains channel coding defining the framing and structuring of the IMBE and other data for transmission, and a particular modulation scheme called C4FM/CQPSK.
The P25 CAI can be used in conventional systems as well as for carrying the voice traffic on a P24 standard trunked system.
Motorola has also used the P25 CIA to send voice traffic on their later digital capable SmartNet/SmartZone systems.

4) "Astro 25" is a Motorola proprietary term that refers to a particular type of trunked radio system. The terms "P25" (referring to a particular voice encoder method) and "Astro 25" (referring to a particular trunking control system) are not synonymous.

"ASTRO 25" is a brand name. As such they can use it any way they see fit.
In general it refers to their "P25" product line and systems, but more recently they have been using it to refer to the core network that supports their P25 trunked systems. This includes that network even when it is supporting a non-P25 system such as a data system.
SO, . . . like any "brand name" done try to be overly specific as to what it means or you will be wrong.
"P25" is a set of standards that includes the over the air interface (P25 CAI), a standardized trunking protocol, a standardized secure protocol, several standardized interface specifications, a soon to be released additional CAI defining a 2 slot TDMA protocol, secure, trunking and interface standards with modifications to allow seamless and near seamless inter-operation between the original P25 CIA and the P25 TDMA CAI systems, etc. etc. etc.
Again, "ASTRO 25" does not refer to a particular trunking protocol directly, but as far as trunking goes would imply the standardized "P25" protocol.

Not quite:

Sorry, Seems you are "Not quite" right.