OutOfMemoryException while trying to send large json data to server in android?

I am trying to send multiple Json string[each 1 MB] at a time to PHP Server. When i tried to send 10 records its working fine. But if it exceeds 20 records it says OutOfMemoryException. I seen that android memory size limit t0 15MB - 16MB. But haven't got any clue how to resolve this, I am using the below code to send multiple records at a time.

 /** Upload Data*/
private void submitUploadData(String url, Map<String, String> param)
        throws IOException {
    URL siteUrl;
    try {
        siteUrl = new URL(url);
        HttpURLConnection conn = (HttpURLConnection) siteUrl
                .openConnection();
        conn.setRequestMethod("POST");
        conn.setDoOutput(true);
        conn.setDoInput(true);

        DataOutputStream out = new DataOutputStream(conn.getOutputStream());
        String content1 = ""; 

        Set getkey = param.keySet();
        Iterator keyIter = getkey.iterator();
        String content = "";
        for (int i = 0; keyIter.hasNext(); i++) {
            Object key = keyIter.next();
            if (i != 0) {
                content += "&"; //Crashing here
            }
            content += key + "=" + param.get(key); //Crashing here
            System.out.println("Content" + content);
        }

        System.out.println(content);
        out.writeBytes(content.trim());
        out.flush();
        out.close();

        BufferedReader in = new BufferedReader(new InputStreamReader(
                conn.getInputStream()));
        String jsonresponse = "";
        while ((jsonresponse = in.readLine()) != null) {
            System.out.println(jsonresponse);   
            if(!jsonresponse.equals("Authorisation Successful")){
            updateUploadRecords(jsonresponse);}

        }
        in.close();  

    } catch (MalformedURLException e) {
        e.printStackTrace();
    } 
}