Very slow speed on cellular

Hi all, I’m using the Cellular module with the “TCP Cellular Radio Driver” provided on CodePlex.

The best baudrate I can get is… 1Kb/Sec.

I have a Hydra connected on the cellular, and nothing else onboard (for the moment).

I build a byte array in memory and while initialized, I loop on it’s sending :

 Debug.Print("1 - "+DateTime.Now);
            byte[] bt = new byte[1024 * 50];
            Debug.Print("2 - " + DateTime.Now);
            for (int i = 0; i < bt.Length; i++) bt[i] = (byte)(char)'A';
            Debug.Print("3 - " + DateTime.Now);
            string test = new string(System.Text.Encoding.UTF8.GetChars(bt));
            while (true)
                Debug.Print("4 - " + DateTime.Now);
                Debug.Print("5 - " + DateTime.Now);

As shown in the attached picture, I always get 1024 byte packets every seconds.

Am I doing something wrong or is it the best rate available ?

Thx for your help !

Debug prints will slow you down a lot. And you’re doing 2x writes per send, so that will skew you data a bit.

Have you looked at the code behind CManager?

Hi Skewworks,

Why do you say I’m writing datas 2 times ? I’m looping on sending to test the bandwidth.

As shown in the console, I measure what I effectively received from the network, and with 50Kb sent at one time, I only receive 1024 bytes packets until the full message has been transmitted.

It takes around 30s to send the 50Kb through the cellular.

I did debug in the driver, but I haven’t seen anything special

Hi Andre, I totally understand that, but it’s not the problem;

My test packet is a 50Kb one. and for the execution of just that line “CManager.SendData(test);” it takes more than 30s and my server is receiving by packet of 1024 bytes

What speeds are you expecting?

The GPRS module using the SIM900 is only quad band so max would be 384Kbps if you have a good signal connection.

I have you checked what the actual connection you have is? GPRS modems jump around to match the signal and the network. You see the same on your phone.

@ Dave : I’m expecting a 50Kb/s

With the same SIM card, on my laptop & on my phone I’m connected in 3G or LTE, with full network connectivity

But in fact I don’t think that it’s a network problem because 1Kb/Sec is less than any carriage mode.
I’m more expecting a problem with the cellular module, may be I have to do something to increase the power available on the module, or configure something, I don’t know.
May be the Hydra can’t handle more than 1024Kb/Sec in serial mode ?

But I’m pretty sure that this rate is abnormally slow.

Anybody ?

What does your receiver code look like?


the server is one I often use :

Server “Core” :

 private void ProcessRequest()
                const int c_microsecondsPerSecond = 1000000;

                using (clientSocket)
                    while (true)
                            if (clientSocket.Poll(5 * c_microsecondsPerSecond,SelectMode.SelectRead))
                                if (clientSocket.Available == 0)   break;

                                byte[] buffer = new byte[clientSocket.Available];
                                int bytesRead = clientSocket.Receive(buffer, clientSocket.Available,SocketFlags.None);

                                byte[] data = new byte[bytesRead];
                                buffer.CopyTo(data, 0);

                                DataReceivedEventArgs args = new DataReceivedEventArgs(clientSocket.LocalEndPoint,clientSocket.RemoteEndPoint, data);

                                if (args.ResponseData != null) clientSocket.Send(args.ResponseData);

                                if (args.Close)   break;
                        catch (Exception ex)

Application Handle :

static void Start()
       _server = new TcpSocketServer(9999);
       _server.DataReceived += _server_DataReceived;

static void _server_DataReceived(object sender, DataReceivedEventArgs e)
       Console.WriteLine(DateTime.Now.ToString()+" - "+ e.Data.Length);

That’s all the code use to test the remote side